Modify test case to include newline characters in TestCase summary

these will end up in email Subject: header and that causes a traceback:

django/core/mail/message.py in forbid_multi_line_headers at line 60:

def forbid_multi_line_headers(name, val, encoding):

    """Forbid multi-line headers to prevent header injection."""

    encoding = encoding or settings.DEFAULT_CHARSET

    val = str(val)  # val may be lazy

    if "\n" in val or "\r" in val:

        raise BadHeaderError(

            "Header values can't contain newlines (got %r for header %r)" % (val, name)

        )

tcms/testcases/tests/test_models.py

@@ -106,14 +106,19 @@ def setUpTestData(cls):
 
     @patch("tcms.core.utils.mailto.send_mail")
     def test_send_mail_to_case_author(self, send_mail):
-        self.case.summary = "New summary for running test"
+        # note: includes \n and \r characters
+        self.case.summary = "New summary\n for\r running test"
         self.case.save()
 
         expected_subject, expected_body = history_email_for(
             self.case, self.case.summary
         )
         recipients = get_case_notification_recipients(self.case)
 
+        # make sure subject doesn't result in a multi-line header
+        self.assertEqual(expected_subject.find("\n"), -1)
+        self.assertEqual(expected_subject.find("\r"), -1)
+
         # Verify notification mail
         send_mail.assert_called_once_with(
             settings.EMAIL_SUBJECT_PREFIX + expected_subject,