Drop support for Python 3.6 and old urllib3

anymail/backends/mailgun.py

@@ -1,33 +1,12 @@
 from datetime import datetime
-from email.utils import encode_rfc2231
 from urllib.parse import quote
 
-from requests import Request
-
 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.)
-# See MailgunPayload.get_request_params for info (and a workaround on older versions).
-# (Note: when this workaround is removed, please also remove "old_urllib3" tox envs.)
-def is_requests_rfc_5758_compliant():
-    request = Request(
-        method="POST",
-        url="https://www.example.com",
-        files=[("attachment", ("\N{NOT SIGN}.txt", "test", "text/plain"))],
-    )
-    prepared = request.prepare()
-    form_data = prepared.body  # bytes
-    return b"filename*=" not in form_data
-
-
-REQUESTS_IS_RFC_7578_COMPLIANT = is_requests_rfc_5758_compliant()
-
-
 class EmailBackend(AnymailRequestsBackend):
     """
     Mailgun API Email Backend
@@ -163,37 +142,6 @@ class MailgunPayload(RequestsPayload):
             )
         return "%s/messages" % quote(self.sender_domain, safe="")
 
-    def get_request_params(self, 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)
-        ]
-        if non_ascii_filenames and not REQUESTS_IS_RFC_7578_COMPLIANT:
-            # Workaround https://github.com/requests/requests/issues/4652:
-            # Mailgun expects RFC 7578 compliant multipart/form-data, and is confused
-            # by Requests/urllib3's improper use of RFC 2231 encoded filename parameters
-            # ("filename*=utf-8''...") in Content-Disposition headers.
-            # The workaround is to pre-generate the (non-compliant) form-data body, and
-            # replace 'filename*={RFC 2231 encoded}' with 'filename="{UTF-8 bytes}"'.
-            # Replace _only_ filenames that will be problems (not all "filename*=...")
-            # to minimize potential side effects--e.g., in attached messages that might
-            # have their own attachments with (correctly) RFC 2231 encoded filenames.
-            prepared = Request(**params).prepare()
-            form_data = prepared.body  # bytes
-            for filename in non_ascii_filenames:  # text
-                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'"',
-                )
-            params["data"] = form_data
-            # Content-Type: multipart/form-data; boundary=...
-            params["headers"]["Content-Type"] = prepared.headers["Content-Type"]
-            params["files"] = None  # these are now in the form_data body
-        return params
-
     def serialize_data(self):
         self.populate_recipient_variables()
         return self.data