Drop Python 2 and Django 1.11 support

Minimum supported versions are now Django 2.0, Python 3.5.

This touches a lot of code, to:
* Remove obsolete portability code and workarounds
  (six, backports of email parsers, test utils, etc.)
* Use Python 3 syntax (class defs, raise ... from, etc.)
* Correct inheritance for mixin classes
* Fix outdated docs content and links
* Suppress Python 3 "unclosed SSLSocket" ResourceWarnings
  that are beyond our control (in integration tests due to boto3, 
  python-sparkpost)

anymail/backends/amazon_ses.py

@@ -1,10 +1,6 @@
 from email.charset import Charset, QP
-from email.header import Header
-from email.mime.base import MIMEBase
 from email.mime.text import MIMEText
 
-from django.core.mail import BadHeaderError
-
 from .base import AnymailBaseBackend, BasePayload
 from .._version import __version__
 from ..exceptions import AnymailAPIError, AnymailImproperlyInstalled
@@ -15,42 +11,14 @@ try:
     import boto3
     from botocore.client import Config
     from botocore.exceptions import BotoCoreError, ClientError, ConnectionError
-except ImportError:
-    raise AnymailImproperlyInstalled(missing_package='boto3', backend='amazon_ses')
+except ImportError as err:
+    raise AnymailImproperlyInstalled(missing_package='boto3', backend='amazon_ses') from err
 
 
 # boto3 has several root exception classes; this is meant to cover all of them
 BOTO_BASE_ERRORS = (BotoCoreError, ClientError, ConnectionError)
 
 
-# Work around Python 2 bug in email.message.Message.to_string, where long headers
-# containing commas or semicolons get an extra space inserted after every ',' or ';'
-# not already followed by a space. https://bugs.python.org/issue25257
-if Header("test,Python2,header,comma,bug", maxlinelen=20).encode() == "test,Python2,header,comma,bug":
-    # no workaround needed
-    HeaderBugWorkaround = None
-
-    def add_header(message, name, val):
-        message[name] = val
-
-else:
-    # workaround: custom Header subclass that won't consider ',' and ';' as folding candidates
-
-    class HeaderBugWorkaround(Header):
-        def encode(self, splitchars=' ', **kwargs):  # only split on spaces, rather than splitchars=';, '
-            return Header.encode(self, splitchars, **kwargs)
-
-    def add_header(message, name, val):
-        # Must bypass Django's SafeMIMEMessage.__set_item__, because its call to
-        # forbid_multi_line_headers converts the val back to a str, undoing this
-        # workaround. That makes this code responsible for sanitizing val:
-        if '\n' in val or '\r' in val:
-            raise BadHeaderError("Header values can't contain newlines (got %r for header %r)" % (val, name))
-        val = HeaderBugWorkaround(val, header_name=name)
-        assert isinstance(message, MIMEBase)
-        MIMEBase.__setitem__(message, name, val)
-
-
 class EmailBackend(AnymailBaseBackend):
     """
     Amazon SES Email Backend (using boto3)
@@ -60,7 +28,7 @@ class EmailBackend(AnymailBaseBackend):
 
     def __init__(self, **kwargs):
         """Init options from Django settings"""
-        super(EmailBackend, self).__init__(**kwargs)
+        super().__init__(**kwargs)
         # AMAZON_SES_CLIENT_PARAMS is optional - boto3 can find credentials several other ways
         self.session_params, self.client_params = _get_anymail_boto3_params(kwargs=kwargs)
         self.configuration_set_name = get_anymail_setting("configuration_set_name", esp_name=self.esp_name,
@@ -77,6 +45,8 @@ class EmailBackend(AnymailBaseBackend):
         except BOTO_BASE_ERRORS:
             if not self.fail_silently:
                 raise
+        else:
+            return True  # created client
 
     def close(self):
         if self.client is None:
@@ -98,7 +68,7 @@ class EmailBackend(AnymailBaseBackend):
         except BOTO_BASE_ERRORS as err:
             # ClientError has a response attr with parsed json error response (other errors don't)
             raise AnymailAPIError(str(err), backend=self, email_message=message, payload=payload,
-                                  response=getattr(err, 'response', None), raised_from=err)
+                                  response=getattr(err, 'response', None)) from err
         return response
 
     def parse_recipient_status(self, response, payload, message):
@@ -125,12 +95,9 @@ class AmazonSESBasePayload(BasePayload):
 
 class AmazonSESSendRawEmailPayload(AmazonSESBasePayload):
     def init_payload(self):
-        super(AmazonSESSendRawEmailPayload, self).init_payload()
+        super().init_payload()
         self.all_recipients = []
         self.mime_message = self.message.message()
-        if HeaderBugWorkaround and "Subject" in self.mime_message:
-            # (message.message() will have already checked subject for BadHeaderError)
-            self.mime_message.replace_header("Subject", HeaderBugWorkaround(self.message.subject))
 
         # Work around an Amazon SES bug where, if all of:
         #   - the message body (text or html) contains non-ASCII characters
@@ -165,7 +132,7 @@ class AmazonSESSendRawEmailPayload(AmazonSESBasePayload):
         except (KeyError, TypeError) as err:
             raise AnymailAPIError(
                 "%s parsing Amazon SES send result %r" % (str(err), response),
-                backend=self.backend, email_message=self.message, payload=self)
+                backend=self.backend, email_message=self.message, payload=self) from None
 
         recipient_status = AnymailRecipientStatus(message_id=message_id, status="queued")
         return {recipient.addr_spec: recipient_status for recipient in self.all_recipients}
@@ -248,14 +215,14 @@ class AmazonSESSendRawEmailPayload(AmazonSESBasePayload):
         # (See "How do message tags work?" in https://aws.amazon.com/blogs/ses/introducing-sending-metrics/
         # and https://forums.aws.amazon.com/thread.jspa?messageID=782922.)
         # To support reliable retrieval in webhooks, just use custom headers for metadata.
-        add_header(self.mime_message, "X-Metadata", self.serialize_json(metadata))
+        self.mime_message["X-Metadata"] = self.serialize_json(metadata)
 
     def set_tags(self, tags):
         # See note about Amazon SES Message Tags and custom headers in set_metadata above.
         # To support reliable retrieval in webhooks, use custom headers for tags.
         # (There are no restrictions on number or content for custom header tags.)
         for tag in tags:
-            add_header(self.mime_message, "X-Tag", tag)  # creates multiple X-Tag headers, one per tag
+            self.mime_message.add_header("X-Tag", tag)  # creates multiple X-Tag headers, one per tag
 
         # Also *optionally* pass a single Message Tag if the AMAZON_SES_MESSAGE_TAG_NAME
         # Anymail setting is set (default no). The AWS API restricts tag content in this case.
@@ -278,7 +245,7 @@ class AmazonSESSendRawEmailPayload(AmazonSESBasePayload):
 
 class AmazonSESSendBulkTemplatedEmailPayload(AmazonSESBasePayload):
     def init_payload(self):
-        super(AmazonSESSendBulkTemplatedEmailPayload, self).init_payload()
+        super().init_payload()
         # late-bind recipients and merge_data in call_send_api
         self.recipients = {"to": [], "cc": [], "bcc": []}
         self.merge_data = {}
@@ -311,7 +278,7 @@ class AmazonSESSendBulkTemplatedEmailPayload(AmazonSESBasePayload):
         except (KeyError, TypeError) as err:
             raise AnymailAPIError(
                 "%s parsing Amazon SES send result %r" % (str(err), response),
-                backend=self.backend, email_message=self.message, payload=self)
+                backend=self.backend, email_message=self.message, payload=self) from None
 
         to_addrs = [to.addr_spec for to in self.recipients["to"]]
         if len(anymail_statuses) != len(to_addrs):

anymail/backends/base.py

@@ -1,7 +1,6 @@
 import json
 from datetime import date, datetime
 
-import six
 from django.conf import settings
 from django.core.mail.backends.base import BaseEmailBackend
 from django.utils.timezone import is_naive, get_current_timezone, make_aware, utc
@@ -23,7 +22,7 @@ class AnymailBaseBackend(BaseEmailBackend):
     """
 
     def __init__(self, *args, **kwargs):
-        super(AnymailBaseBackend, self).__init__(*args, **kwargs)
+        super().__init__(*args, **kwargs)
 
         self.ignore_unsupported_features = get_anymail_setting('ignore_unsupported_features',
                                                                kwargs=kwargs, default=False)
@@ -207,7 +206,7 @@ class AnymailBaseBackend(BaseEmailBackend):
                                   (self.__class__.__module__, self.__class__.__name__))
 
 
-class BasePayload(object):
+class BasePayload:
     # Listing of EmailMessage/EmailMultiAlternatives attributes
     # to process into Payload. Each item is in the form:
     #   (attr, combiner, converter)
@@ -365,7 +364,7 @@ class BasePayload(object):
         #   TypeError: must be str, not list
         #   TypeError: can only concatenate list (not "str") to list
         #   TypeError: Can't convert 'list' object to str implicitly
-        if isinstance(value, six.string_types) or is_lazy(value):
+        if isinstance(value, str) or is_lazy(value):
             raise TypeError('"{attr}" attribute must be a list or other iterable'.format(attr=attr))
 
     #
@@ -538,7 +537,7 @@ class BasePayload(object):
         except TypeError as err:
             # Add some context to the "not JSON serializable" message
             raise AnymailSerializationError(orig_err=err, email_message=self.message,
-                                            backend=self.backend, payload=self)
+                                            backend=self.backend, payload=self) from None
 
     @staticmethod
     def _json_default(o):

anymail/backends/base_requests.py

@@ -1,13 +1,11 @@
-from __future__ import print_function
+from urllib.parse import urljoin
 
 import requests
-import six
-from six.moves.urllib.parse import urljoin
 
 from anymail.utils import get_anymail_setting
 from .base import AnymailBaseBackend, BasePayload
-from ..exceptions import AnymailRequestsAPIError
 from .._version import __version__
+from ..exceptions import AnymailRequestsAPIError
 
 
 class AnymailRequestsBackend(AnymailBaseBackend):
@@ -19,7 +17,7 @@ class AnymailRequestsBackend(AnymailBaseBackend):
         """Init options from Django settings"""
         self.api_url = api_url
         self.timeout = get_anymail_setting('requests_timeout', kwargs=kwargs, default=30)
-        super(AnymailRequestsBackend, self).__init__(**kwargs)
+        super().__init__(**kwargs)
         self.session = None
 
     def open(self):
@@ -57,7 +55,7 @@ class AnymailRequestsBackend(AnymailBaseBackend):
                 "Session has not been opened in {class_name}._send. "
                 "(This is either an implementation error in {class_name}, "
                 "or you are incorrectly calling _send directly.)".format(class_name=class_name))
-        return super(AnymailRequestsBackend, self)._send(message)
+        return super()._send(message)
 
     def post_to_esp(self, payload, message):
         """Post payload to ESP send API endpoint, and return the raw response.
@@ -78,7 +76,7 @@ class AnymailRequestsBackend(AnymailBaseBackend):
             exc_class = type('AnymailRequestsAPIError', (AnymailRequestsAPIError, type(err)), {})
             raise exc_class(
                 "Error posting to %s:" % params.get('url', '<missing url>'),
-                raised_from=err, email_message=message, payload=payload)
+                email_message=message, payload=payload) from err
         self.raise_for_status(response, payload, message)
         return response
 
@@ -100,10 +98,10 @@ class AnymailRequestsBackend(AnymailBaseBackend):
         """
         try:
             return response.json()
-        except ValueError:
+        except ValueError as err:
             raise AnymailRequestsAPIError("Invalid JSON in %s API response" % self.esp_name,
                                           email_message=message, payload=payload, response=response,
-                                          backend=self)
+                                          backend=self) from err
 
     @staticmethod
     def _dump_api_request(response, **kwargs):
@@ -113,22 +111,22 @@ class AnymailRequestsBackend(AnymailBaseBackend):
         # If you need the raw bytes, configure HTTPConnection logging as shown
         # in http://docs.python-requests.org/en/v3.0.0/api/#api-changes)
         request = response.request  # a PreparedRequest
-        print(u"\n===== Anymail API request")
-        print(u"{method} {url}\n{headers}".format(
+        print("\n===== Anymail API request")
+        print("{method} {url}\n{headers}".format(
             method=request.method, url=request.url,
-            headers=u"".join(u"{header}: {value}\n".format(header=header, value=value)
-                             for (header, value) in request.headers.items()),
+            headers="".join("{header}: {value}\n".format(header=header, value=value)
+                            for (header, value) in request.headers.items()),
         ))
         if request.body is not None:
-            body_text = (request.body if isinstance(request.body, six.text_type)
+            body_text = (request.body if isinstance(request.body, str)
                          else request.body.decode("utf-8", errors="replace")
                          ).replace("\r\n", "\n")
             print(body_text)
-        print(u"\n----- Response")
-        print(u"HTTP {status} {reason}\n{headers}\n{body}".format(
+        print("\n----- Response")
+        print("HTTP {status} {reason}\n{headers}\n{body}".format(
             status=response.status_code, reason=response.reason,
-            headers=u"".join(u"{header}: {value}\n".format(header=header, value=value)
-                             for (header, value) in response.headers.items()),
+            headers="".join("{header}: {value}\n".format(header=header, value=value)
+                            for (header, value) in response.headers.items()),
             body=response.text,  # Let Requests decode body content for us
         ))
 
@@ -145,7 +143,7 @@ class RequestsPayload(BasePayload):
         self.headers = headers
         self.files = files
         self.auth = auth
-        super(RequestsPayload, self).__init__(message, defaults, backend)
+        super().__init__(message, defaults, backend)
 
     def get_request_params(self, api_url):
         """Returns a dict of requests.request params that will send payload to the ESP.

anymail/backends/mailgun.py

@@ -1,15 +1,14 @@
 from datetime import datetime
 from email.utils import encode_rfc2231
-from six.moves.urllib.parse import quote
+from urllib.parse import quote
 
 from requests import Request
 
-from ..exceptions import AnymailRequestsAPIError, AnymailError
+from .base_requests import AnymailRequestsBackend, RequestsPayload
+from ..exceptions import AnymailError, AnymailRequestsAPIError
 from ..message import AnymailRecipientStatus
 from ..utils import get_anymail_setting, rfc2822date
 
-from .base_requests import AnymailRequestsBackend, RequestsPayload
-
 
 # Feature-detect whether requests (urllib3) correctly uses RFC 7578 encoding for non-
 # ASCII filenames in Content-Disposition headers. (This was fixed in urllib3 v1.25.)
@@ -17,7 +16,7 @@ from .base_requests import AnymailRequestsBackend, RequestsPayload
 # (Note: when this workaround is removed, please also remove the "old_urllib3" tox envs.)
 def is_requests_rfc_5758_compliant():
     request = Request(method='POST', url='https://www.example.com',
-                      files=[('attachment', (u'\N{NOT SIGN}.txt', 'test', 'text/plain'))])
+                      files=[('attachment', ('\N{NOT SIGN}.txt', 'test', 'text/plain'))])
     prepared = request.prepare()
     form_data = prepared.body  # bytes
     return b'filename*=' not in form_data
@@ -43,7 +42,7 @@ class EmailBackend(AnymailRequestsBackend):
                                       default="https://api.mailgun.net/v3")
         if not api_url.endswith("/"):
             api_url += "/"
-        super(EmailBackend, self).__init__(api_url, **kwargs)
+        super().__init__(api_url, **kwargs)
 
     def build_message_payload(self, message, defaults):
         return MailgunPayload(message, defaults, self)
@@ -62,10 +61,10 @@ class EmailBackend(AnymailRequestsBackend):
         try:
             message_id = parsed_response["id"]
             mailgun_message = parsed_response["message"]
-        except (KeyError, TypeError):
+        except (KeyError, TypeError) as err:
             raise AnymailRequestsAPIError("Invalid Mailgun API response format",
                                           email_message=message, payload=payload, response=response,
-                                          backend=self)
+                                          backend=self) from err
         if not mailgun_message.startswith("Queued"):
             raise AnymailRequestsAPIError("Unrecognized Mailgun API message '%s'" % mailgun_message,
                                           email_message=message, payload=payload, response=response,
@@ -89,7 +88,7 @@ class MailgunPayload(RequestsPayload):
         self.merge_metadata = {}
         self.to_emails = []
 
-        super(MailgunPayload, self).__init__(message, defaults, backend, auth=auth, *args, **kwargs)
+        super().__init__(message, defaults, backend, auth=auth, *args, **kwargs)
 
     def get_api_endpoint(self):
         if self.sender_domain is None:
@@ -105,7 +104,7 @@ class MailgunPayload(RequestsPayload):
         return "%s/messages" % quote(self.sender_domain, safe='')
 
     def get_request_params(self, api_url):
-        params = super(MailgunPayload, self).get_request_params(api_url)
+        params = super().get_request_params(api_url)
         non_ascii_filenames = [filename
                                for (field, (filename, content, mimetype)) in params["files"]
                                if filename is not None and not isascii(filename)]
@@ -122,9 +121,7 @@ class MailgunPayload(RequestsPayload):
             prepared = Request(**params).prepare()
             form_data = prepared.body  # bytes
             for filename in non_ascii_filenames:  # text
-                rfc2231_filename = encode_rfc2231(  # wants a str (text in PY3, bytes in PY2)
-                    filename if isinstance(filename, str) else filename.encode("utf-8"),
-                    charset="utf-8")
+                rfc2231_filename = encode_rfc2231(filename, charset="utf-8")
                 form_data = form_data.replace(
                     b'filename*=' + rfc2231_filename.encode("utf-8"),
                     b'filename="' + filename.encode("utf-8") + b'"')

anymail/backends/mailjet.py

@@ -1,12 +1,10 @@
 from email.header import Header
-
-from six.moves.urllib.parse import quote
-
-from ..exceptions import AnymailRequestsAPIError
-from ..message import AnymailRecipientStatus, ANYMAIL_STATUSES
-from ..utils import get_anymail_setting, EmailAddress, parse_address_list
+from urllib.parse import quote
 
 from .base_requests import AnymailRequestsBackend, RequestsPayload
+from ..exceptions import AnymailRequestsAPIError
+from ..message import ANYMAIL_STATUSES, AnymailRecipientStatus
+from ..utils import EmailAddress, get_anymail_setting, parse_address_list
 
 
 class EmailBackend(AnymailRequestsBackend):
@@ -25,7 +23,7 @@ class EmailBackend(AnymailRequestsBackend):
                                       default="https://api.mailjet.com/v3")
         if not api_url.endswith("/"):
             api_url += "/"
-        super(EmailBackend, self).__init__(api_url, **kwargs)
+        super().__init__(api_url, **kwargs)
 
     def build_message_payload(self, message, defaults):
         return MailjetPayload(message, defaults, self)
@@ -36,7 +34,7 @@ class EmailBackend(AnymailRequestsBackend):
             raise AnymailRequestsAPIError(
                 "Invalid Mailjet API key or secret",
                 email_message=message, payload=payload, response=response, backend=self)
-        super(EmailBackend, self).raise_for_status(response, payload, message)
+        super().raise_for_status(response, payload, message)
 
     def parse_recipient_status(self, response, payload, message):
         # Mailjet's (v3.0) transactional send API is not covered in their reference docs.
@@ -61,10 +59,10 @@ class EmailBackend(AnymailRequestsBackend):
                     message_id = str(item['MessageID'])
                     email = item['Email']
                     recipient_status[email] = AnymailRecipientStatus(message_id=message_id, status=status)
-        except (KeyError, TypeError):
+        except (KeyError, TypeError) as err:
             raise AnymailRequestsAPIError("Invalid Mailjet API response format",
                                           email_message=message, payload=payload, response=response,
-                                          backend=self)
+                                          backend=self) from err
         # Make sure we ended up with a status for every original recipient
         # (Mailjet only communicates "Sent")
         for recipients in payload.recipients.values():
@@ -88,8 +86,7 @@ class MailjetPayload(RequestsPayload):
         self.metadata = None
         self.merge_data = {}
         self.merge_metadata = {}
-        super(MailjetPayload, self).__init__(message, defaults, backend,
-                                             auth=auth, headers=http_headers, *args, **kwargs)
+        super().__init__(message, defaults, backend, auth=auth, headers=http_headers, *args, **kwargs)
 
     def get_api_endpoint(self):
         return "send"
@@ -153,9 +150,10 @@ class MailjetPayload(RequestsPayload):
                                               parsed.addr_spec)
                 else:
                     parsed = EmailAddress(headers["SenderName"], headers["SenderEmail"])
-            except KeyError:
+            except KeyError as err:
                 raise AnymailRequestsAPIError("Invalid Mailjet template API response",
-                                              email_message=self.message, response=response, backend=self.backend)
+                                              email_message=self.message, response=response,
+                                              backend=self.backend) from err
             self.set_from_email(parsed)
 
     def _format_email_for_mailjet(self, email):

anymail/backends/mandrill.py

@@ -23,7 +23,7 @@ class EmailBackend(AnymailRequestsBackend):
                                       default="https://mandrillapp.com/api/1.0")
         if not api_url.endswith("/"):
             api_url += "/"
-        super(EmailBackend, self).__init__(api_url, **kwargs)
+        super().__init__(api_url, **kwargs)
 
     def build_message_payload(self, message, defaults):
         return MandrillPayload(message, defaults, self)
@@ -40,10 +40,10 @@ class EmailBackend(AnymailRequestsBackend):
                     status = 'unknown'
                 message_id = item.get('_id', None)  # can be missing for invalid/rejected recipients
                 recipient_status[email] = AnymailRecipientStatus(message_id=message_id, status=status)
-        except (KeyError, TypeError):
+        except (KeyError, TypeError) as err:
             raise AnymailRequestsAPIError("Invalid Mandrill API response format",
                                           email_message=message, payload=payload, response=response,
-                                          backend=self)
+                                          backend=self) from err
         return recipient_status
 
 
@@ -69,7 +69,7 @@ class MandrillPayload(RequestsPayload):
 
     def __init__(self, *args, **kwargs):
         self.esp_extra = {}  # late-bound in serialize_data
-        super(MandrillPayload, self).__init__(*args, **kwargs)
+        super().__init__(*args, **kwargs)
 
     def get_api_endpoint(self):
         if 'template_name' in self.data:

anymail/backends/postmark.py

@@ -22,7 +22,7 @@ class EmailBackend(AnymailRequestsBackend):
                                       default="https://api.postmarkapp.com/")
         if not api_url.endswith("/"):
             api_url += "/"
-        super(EmailBackend, self).__init__(api_url, **kwargs)
+        super().__init__(api_url, **kwargs)
 
     def build_message_payload(self, message, defaults):
         return PostmarkPayload(message, defaults, self)
@@ -30,7 +30,7 @@ class EmailBackend(AnymailRequestsBackend):
     def raise_for_status(self, response, payload, message):
         # We need to handle 422 responses in parse_recipient_status
         if response.status_code != 422:
-            super(EmailBackend, self).raise_for_status(response, payload, message)
+            super().raise_for_status(response, payload, message)
 
     def parse_recipient_status(self, response, payload, message):
         # Default to "unknown" status for each recipient, unless/until we find otherwise.
@@ -51,19 +51,19 @@ class EmailBackend(AnymailRequestsBackend):
                 # these fields should always be present
                 error_code = one_response["ErrorCode"]
                 msg = one_response["Message"]
-            except (KeyError, TypeError):
+            except (KeyError, TypeError) as err:
                 raise AnymailRequestsAPIError("Invalid Postmark API response format",
                                               email_message=message, payload=payload, response=response,
-                                              backend=self)
+                                              backend=self) from err
 
             if error_code == 0:
                 # At least partial success, and (some) email was sent.
                 try:
                     message_id = one_response["MessageID"]
-                except KeyError:
+                except KeyError as err:
                     raise AnymailRequestsAPIError("Invalid Postmark API success response format",
                                                   email_message=message, payload=payload,
-                                                  response=response, backend=self)
+                                                  response=response, backend=self) from err
 
                 # Assume all To recipients are "sent" unless proven otherwise below.
                 # (Must use "To" from API response to get correct individual MessageIDs in batch send.)
@@ -157,7 +157,7 @@ class PostmarkPayload(RequestsPayload):
         self.cc_and_bcc_emails = []  # need to track (separately) for parse_recipient_status
         self.merge_data = None
         self.merge_metadata = None
-        super(PostmarkPayload, self).__init__(message, defaults, backend, headers=headers, *args, **kwargs)
+        super().__init__(message, defaults, backend, headers=headers, *args, **kwargs)
 
     def get_api_endpoint(self):
         batch_send = self.is_batch() and len(self.to_emails) > 1
@@ -174,7 +174,7 @@ class PostmarkPayload(RequestsPayload):
                 return "email"
 
     def get_request_params(self, api_url):
-        params = super(PostmarkPayload, self).get_request_params(api_url)
+        params = super().get_request_params(api_url)
         params['headers']['X-Postmark-Server-Token'] = self.server_token
         return params
 

anymail/backends/sendgrid.py

@@ -7,7 +7,7 @@ from requests.structures import CaseInsensitiveDict
 from .base_requests import AnymailRequestsBackend, RequestsPayload
 from ..exceptions import AnymailConfigurationError, AnymailRequestsAPIError, AnymailWarning
 from ..message import AnymailRecipientStatus
-from ..utils import BASIC_NUMERIC_TYPES, Mapping, get_anymail_setting, timestamp, update_deep
+from ..utils import BASIC_NUMERIC_TYPES, Mapping, get_anymail_setting, update_deep
 
 
 class EmailBackend(AnymailRequestsBackend):
@@ -47,7 +47,7 @@ class EmailBackend(AnymailRequestsBackend):
                                       default="https://api.sendgrid.com/v3/")
         if not api_url.endswith("/"):
             api_url += "/"
-        super(EmailBackend, self).__init__(api_url, **kwargs)
+        super().__init__(api_url, **kwargs)
 
     def build_message_payload(self, message, defaults):
         return SendGridPayload(message, defaults, self)
@@ -84,9 +84,7 @@ class SendGridPayload(RequestsPayload):
         http_headers['Authorization'] = 'Bearer %s' % backend.api_key
         http_headers['Content-Type'] = 'application/json'
         http_headers['Accept'] = 'application/json'
-        super(SendGridPayload, self).__init__(message, defaults, backend,
-                                              headers=http_headers,
-                                              *args, **kwargs)
+        super().__init__(message, defaults, backend, headers=http_headers, *args, **kwargs)
 
     def get_api_endpoint(self):
         return "mail/send"
@@ -294,7 +292,7 @@ class SendGridPayload(RequestsPayload):
     def set_send_at(self, send_at):
         # Backend has converted pretty much everything to
         # a datetime by here; SendGrid expects unix timestamp
-        self.data["send_at"] = int(timestamp(send_at))  # strip microseconds
+        self.data["send_at"] = int(send_at.timestamp())  # strip microseconds
 
     def set_tags(self, tags):
         self.data["categories"] = tags

anymail/backends/sendinblue.py

@@ -30,7 +30,7 @@ class EmailBackend(AnymailRequestsBackend):
         )
         if not api_url.endswith("/"):
             api_url += "/"
-        super(EmailBackend, self).__init__(api_url, **kwargs)
+        super().__init__(api_url, **kwargs)
 
     def build_message_payload(self, message, defaults):
         return SendinBluePayload(message, defaults, self)
@@ -53,10 +53,10 @@ class EmailBackend(AnymailRequestsBackend):
             parsed_response = self.deserialize_json_response(response, payload, message)
             try:
                 message_id = parsed_response['messageId']
-            except (KeyError, TypeError):
+            except (KeyError, TypeError) as err:
                 raise AnymailRequestsAPIError("Invalid SendinBlue API response format",
                                               email_message=message, payload=payload, response=response,
-                                              backend=self)
+                                              backend=self) from err
 
         status = AnymailRecipientStatus(message_id=message_id, status="queued")
         return {recipient.addr_spec: status for recipient in payload.all_recipients}
@@ -71,7 +71,7 @@ class SendinBluePayload(RequestsPayload):
         http_headers['api-key'] = backend.api_key
         http_headers['Content-Type'] = 'application/json'
 
-        super(SendinBluePayload, self).__init__(message, defaults, backend, headers=http_headers, *args, **kwargs)
+        super().__init__(message, defaults, backend, headers=http_headers, *args, **kwargs)
 
     def get_api_endpoint(self):
         return "smtp/email"

anymail/backends/sparkpost.py

@@ -1,5 +1,3 @@
-from __future__ import absolute_import  # we want the sparkpost package, not our own module
-
 from .base import AnymailBaseBackend, BasePayload
 from ..exceptions import AnymailAPIError, AnymailImproperlyInstalled, AnymailConfigurationError
 from ..message import AnymailRecipientStatus
@@ -7,8 +5,8 @@ from ..utils import get_anymail_setting
 
 try:
     from sparkpost import SparkPost, SparkPostException
-except ImportError:
-    raise AnymailImproperlyInstalled(missing_package='sparkpost', backend='sparkpost')
+except ImportError as err:
+    raise AnymailImproperlyInstalled(missing_package='sparkpost', backend='sparkpost') from err
 
 
 class EmailBackend(AnymailBaseBackend):
@@ -20,7 +18,7 @@ class EmailBackend(AnymailBaseBackend):
 
     def __init__(self, **kwargs):
         """Init options from Django settings"""
-        super(EmailBackend, self).__init__(**kwargs)
+        super().__init__(**kwargs)
         # SPARKPOST_API_KEY is optional - library reads from env by default
         self.api_key = get_anymail_setting('api_key', esp_name=self.esp_name,
                                            kwargs=kwargs, allow_bare=True, default=None)
@@ -43,7 +41,7 @@ class EmailBackend(AnymailBaseBackend):
                 "You may need to set ANYMAIL = {'SPARKPOST_API_KEY': ...} "
                 "or ANYMAIL_SPARKPOST_API_KEY in your Django settings, "
                 "or SPARKPOST_API_KEY in your environment." % str(err)
-            )
+            ) from err
 
     # Note: SparkPost python API doesn't expose requests session sharing
     # (so there's no need to implement open/close connection management here)
@@ -60,7 +58,7 @@ class EmailBackend(AnymailBaseBackend):
                 str(err), backend=self, email_message=message, payload=payload,
                 response=getattr(err, 'response', None),  # SparkPostAPIException requests.Response
                 status_code=getattr(err, 'status', None),  # SparkPostAPIException HTTP status_code
-            )
+            ) from err
         return response
 
     def parse_recipient_status(self, response, payload, message):
@@ -72,7 +70,7 @@ class EmailBackend(AnymailBaseBackend):
             raise AnymailAPIError(
                 "%s in SparkPost.transmissions.send result %r" % (str(err), response),
                 backend=self, email_message=message, payload=payload,
-            )
+            ) from err
 
         # SparkPost doesn't (yet*) tell us *which* recipients were accepted or rejected.
         # (* looks like undocumented 'rcpt_to_errors' might provide this info.)

anymail/backends/test.py

@@ -25,7 +25,7 @@ class EmailBackend(AnymailBaseBackend):
         # Allow replacing the payload, for testing.
         # (Real backends would generally not implement this option.)
         self._payload_class = kwargs.pop('payload_class', TestPayload)
-        super(EmailBackend, self).__init__(*args, **kwargs)
+        super().__init__(*args, **kwargs)
         if not hasattr(mail, 'outbox'):
             mail.outbox = []  # see django.core.mail.backends.locmem
 
@@ -60,8 +60,8 @@ class EmailBackend(AnymailBaseBackend):
     def parse_recipient_status(self, response, payload, message):
         try:
             return response['recipient_status']
-        except KeyError:
-            raise AnymailAPIError('Unparsable test response')
+        except KeyError as err:
+            raise AnymailAPIError('Unparsable test response') from err
 
 
 class TestPayload(BasePayload):