Mailjet: Don't try to parse non-JSON responses as JSON.

Fixes #409.

CHANGELOG.rst

@@ -43,6 +43,8 @@ Fixes
 * **Mailjet:** Avoid a Mailjet API error when sending an inline image without a
   filename. (Anymail now substitutes ``"attachment"`` for the missing filename.)
   (Thanks to `@chickahoona`_ for reporting the issue.)
+* **Mailjet:** Fix a JSON parsing error on Mailjet 429 "too many requests" API
+  responses. (Thanks to `@rodrigondec`_ for reporting the issue.)
 
 
 v12.0
@@ -1779,6 +1781,7 @@ Features
 .. _@originell: https://github.com/originell
 .. _@puru02: https://github.com/puru02
 .. _@RignonNoel: https://github.com/RignonNoel
+.. _@rodrigondec: https://github.com/rodrigondec
 .. _@sblondon: https://github.com/sblondon
 .. _@scur-iolus: https://github.com/scur-iolus
 .. _@sdarwin: https://github.com/sdarwin

anymail/backends/mailjet.py

@@ -34,7 +34,10 @@ class EmailBackend(AnymailRequestsBackend):
         return MailjetPayload(message, defaults, self)
 
     def raise_for_status(self, response, payload, message):
-        if 400 <= response.status_code <= 499:
+        content_type = (
+            response.headers.get("content-type", "").split(";")[0].strip().lower()
+        )
+        if 400 <= response.status_code <= 499 and content_type == "application/json":
             # Mailjet uses 4xx status codes for partial failure in batch send;
             # we'll determine how to handle below in parse_recipient_status.
             return

tests/test_mailjet_backend.py

@@ -10,6 +10,7 @@ from django.test import SimpleTestCase, override_settings, tag
 
 from anymail.exceptions import (
     AnymailAPIError,
+    AnymailRequestsAPIError,
     AnymailSerializationError,
     AnymailUnsupportedFeature,
 )
@@ -690,8 +691,7 @@ class MailjetBackendAnymailFeatureTests(MailjetBackendMockAPITestCase):
         # Mailjet's v3.1 API will partially fail a batch send, allowing valid emails
         # to go out. The API response doesn't identify the failed email addresses;
         # make sure we represent them correctly in the anymail_status.
-        response_content = json.dumps(
+        response_data = {
-            {
             "Messages": [
                 {
                     "Status": "success",
@@ -724,9 +724,8 @@ class MailjetBackendAnymailFeatureTests(MailjetBackendMockAPITestCase):
                 },
             ]
         }
-        ).encode("utf-8")
         # Mailjet uses 400 for partial success:
-        self.set_mock_response(raw=response_content, status_code=400)
+        self.set_mock_response(json_data=response_data, status_code=400)
         msg = mail.EmailMessage(
             "Subject",
             "Message",
@@ -751,7 +750,7 @@ class MailjetBackendAnymailFeatureTests(MailjetBackendMockAPITestCase):
             msg.anymail_status.recipients["invalid@123.4"].message_id, None
         )
         self.assertEqual(msg.anymail_status.message_id, {"12345678901234500", None})
-        self.assertEqual(msg.anymail_status.esp_response.content, response_content)
+        self.assertEqual(msg.anymail_status.esp_response.json(), response_data)
 
     # noinspection PyUnresolvedReferences
     def test_send_failed_anymail_status(self):
@@ -764,6 +763,18 @@ class MailjetBackendAnymailFeatureTests(MailjetBackendMockAPITestCase):
         self.assertEqual(self.message.anymail_status.recipients, {})
         self.assertIsNone(self.message.anymail_status.esp_response)
 
+    def test_non_json_error(self):
+        """429 (and other?) errors don't have a json payload"""
+        self.set_mock_response(
+            status_code=429, raw=b"Rate limit exceeded", content_type="text/html"
+        )
+        with self.assertRaisesRegex(
+            AnymailRequestsAPIError,
+            r"^Mailjet API response 429 .*Rate limit exceeded.*",
+        ) as cm:
+            self.message.send()
+        self.assertNotIn("Invalid JSON", str(cm.exception))
+
     # noinspection PyUnresolvedReferences
     def test_send_unparsable_response(self):
         """