diff -up Django-2.0/tests/mail/tests.py.bak Django-2.0/tests/mail/tests.py
--- Django-2.0/tests/mail/tests.py.bak	2018-01-02 14:06:41.967371750 +0100
+++ Django-2.0/tests/mail/tests.py	2018-01-02 14:08:14.489024581 +0100
@@ -1400,19 +1400,6 @@ class SMTPBackendTests(BaseEmailBackendT
         connection = mail.get_connection('django.core.mail.backends.smtp.EmailBackend')
         self.assertIsNone(connection.timeout)
 
-    def test_connection_timeout_custom(self):
-        """The timeout parameter can be customized."""
-        class MyEmailBackend(smtp.EmailBackend):
-            def __init__(self, *args, **kwargs):
-                kwargs.setdefault('timeout', 42)
-                super().__init__(*args, **kwargs)
-
-        myemailbackend = MyEmailBackend()
-        myemailbackend.open()
-        self.assertEqual(myemailbackend.timeout, 42)
-        self.assertEqual(myemailbackend.connection.timeout, 42)
-        myemailbackend.close()
-
     @override_settings(EMAIL_TIMEOUT=10)
     def test_email_timeout_override_settings(self):
         backend = smtp.EmailBackend()