Fixed #30058 -- Made SMTP EmailBackend.send_messages() return 0 for empty/error cases.

django/core/mail/backends/smtp.py

@@ -98,13 +98,13 @@ class EmailBackend(BaseEmailBackend):
         messages sent.
         """
         if not email_messages:
-            return
+            return 0
         with self._lock:
             new_conn_created = self.open()
             if not self.connection or new_conn_created is None:
                 # We failed silently on open().
                 # Trying to send would be pointless.
-                return
+                return 0
             num_sent = 0
             for message in email_messages:
                 sent = self._send(message)