Fixed #36119 -- Fixed UnicodeEncodeError when attaching a file with 8bit Content-Transfer-Encoding.

tests/mail/tests.py

@@ -913,6 +913,30 @@ class MailTests(MailTestsMixin, SimpleTestCase):
         self.assertEqual(content, b"\xff")
         self.assertEqual(mimetype, "application/octet-stream")
 
+    def test_attach_8bit_rfc822_message_non_ascii(self):
+        """
+        Attaching a message that uses 8bit content transfer encoding for
+        non-ASCII characters should not raise a UnicodeEncodeError (#36119).
+        """
+        attachment = dedent(
+            """\
+            Subject: A message using 8bit CTE
+            Content-Type: text/plain; charset=utf-8
+            Content-Transfer-Encoding: 8bit
+
+            ¡8-bit content!
+            """
+        ).encode()
+        email = EmailMessage()
+        email.attach("attachment.eml", attachment, "message/rfc822")
+        attachments = self.get_raw_attachments(email)
+        self.assertEqual(len(attachments), 1)
+        self.assertEqual(attachments[0].get_content_type(), "message/rfc822")
+        attached_message = attachments[0].get_content()
+        self.assertEqual(attached_message.get_content().rstrip(), "¡8-bit content!")
+        self.assertEqual(attached_message["Content-Transfer-Encoding"], "8bit")
+        self.assertEqual(attached_message.get_content_type(), "text/plain")
+
     def test_attach_mime_image(self):
         """
         EmailMessage.attach() docs: "You can pass it