Ticket #10314: assert_msg_patch

diff --git a/django/test/testcases.py b/django/test/testcases.py
index 8c73c63..dc9aa81 100644
--- a/django/test/testcases.py
+++ b/django/test/testcases.py
@@ -203,6 +203,24 @@ class DocTestRunner(doctest.DocTestRunner):
         # side effects on other tests.
         transaction.rollback_unless_managed()
 
+
+import sys
+from django.utils.decorators import auto_adapt_to_methods, wraps
+def custom_assert_message(assert_method):
+    """
+    Decorator for assert methods which adds a msg parameter. This parameter
+    will replace the message in any AssertionErrors raised.
+    """
+    def _wrapped_method(*args, **kwargs):
+        msg = kwargs.pop('msg', None)
+        try:
+            return assert_method(*args, **kwargs)
+        except AssertionError, e:
+            raise e.__class__(msg or str(e)), None, sys.exc_info()[2]
+    return wraps(assert_method)(_wrapped_method)
+custom_assert_message = auto_adapt_to_methods(custom_assert_message)
+
+
 class TransactionTestCase(unittest.TestCase):
     def _pre_setup(self):
         """Performs any pre-test setup. This includes:
@@ -343,6 +361,7 @@ class TransactionTestCase(unittest.TestCase):
         else:
             self.failUnless(real_count != 0,
                             "Couldn't find '%s' in response" % text)
+    assertContains = custom_assert_message(assertContains)
 
     def assertNotContains(self, response, text, status_code=200):
         """
@@ -356,6 +375,7 @@ class TransactionTestCase(unittest.TestCase):
         text = smart_str(text, response._charset)
         self.assertEqual(response.content.count(text),
              0, "Response should not contain '%s'" % text)
+    assertNotContains = custom_assert_message(assertNotContains)
 
     def assertFormError(self, response, form, field, errors):
         """
@@ -403,6 +423,7 @@ class TransactionTestCase(unittest.TestCase):
         if not found_form:
             self.fail("The form '%s' was not used to render the response" %
                           form)
+    assertFormError = custom_assert_message(assertFormError)
 
     def assertTemplateUsed(self, response, template_name):
         """
@@ -416,6 +437,7 @@ class TransactionTestCase(unittest.TestCase):
             (u"Template '%s' was not a template used to render the response."
              u" Actual template(s) used: %s") % (template_name,
                                                  u', '.join(template_names)))
+    assertTemplateUsed = custom_assert_message(assertTemplateUsed)
 
     def assertTemplateNotUsed(self, response, template_name):
         """
@@ -426,6 +448,7 @@ class TransactionTestCase(unittest.TestCase):
         self.failIf(template_name in template_names,
             (u"Template '%s' was used unexpectedly in rendering the"
              u" response") % template_name)
+    assertTemplateNotUsed = custom_assert_message(assertTemplateNotUsed)
 
 class TestCase(TransactionTestCase):
     """
diff --git a/tests/regressiontests/test_client_regress/models.py b/tests/regressiontests/test_client_regress/models.py
index be2cb8f..f26b0e9 100644
--- a/tests/regressiontests/test_client_regress/models.py
+++ b/tests/regressiontests/test_client_regress/models.py
@@ -79,6 +79,34 @@ class AssertContainsTests(TestCase):
         self.assertNotContains(r, u'はたけ')
         self.assertNotContains(r, '\xe3\x81\xaf\xe3\x81\x9f\xe3\x81\x91'.decode('utf-8'))
 
+    def test_custom_message(self):
+        "Custom message argument is used correctly."
+        url = '/test_client_regress/no_template_view/'
+        response = self.client.get(url)
+        m = 'custom message'
+
+        try:
+            self.assertContains(response, 'never', msg=m)
+        except AssertionError, e:
+            self.assertEquals(str(e), m)
+        try:
+            self.assertContains(response, 'never', 1, msg=m)
+        except AssertionError, e:
+            self.assertEquals(str(e), m)
+        try:
+            self.assertContains(response, 'text', status_code=999, msg=m)
+        except AssertionError, e:
+            self.assertEquals(str(e), m)
+
+        try:
+             self.assertNotContains(response, 'once', msg=m)
+        except AssertionError, e:
+            self.assertEquals(str(e), m)
+        try:
+             self.assertNotContains(response, 'once', status_code=999, msg=m)
+        except AssertionError, e:
+            self.assertEquals(str(e), m)
+
 class AssertTemplateUsedTests(TestCase):
     fixtures = ['testdata.json']