[1.7.x] Fixed #24903 -- Fixed assertRaisesMessage on Python 2.7.10.

A regression found in in Python 2.7.10 rc1 wasn't reverted for the final
release: https://bugs.python.org/issue24134

Backport of two commits from master:
* c2bc1ce
* e89c3a4

django/test/testcases.py

@@ -558,21 +558,25 @@ def assertTemplateNotUsed(self, response=None, template_name=None, msg_prefix=''
             msg_prefix + "Template '%s' was used unexpectedly in rendering"
             " the response" % template_name)
 
-    def assertRaisesMessage(self, expected_exception, expected_message,
-                           callable_obj=None, *args, **kwargs):
+    def assertRaisesMessage(self, expected_exception, expected_message, *args, **kwargs):
         """
         Asserts that the message in a raised exception matches the passed
         value.
 
         Args:
             expected_exception: Exception class expected to be raised.
             expected_message: expected error message string value.
-            callable_obj: Function to be called.
-            args: Extra args.
+            args: Function to be called and extra positional args.
             kwargs: Extra kwargs.
         """
+        # callable_obj was a documented kwarg in older version of Django, but
+        # had to be removed due to a bad fix for http://bugs.python.org/issue24134
+        # inadvertently making its way into Python 2.7.10.
+        callable_obj = kwargs.pop('callable_obj', None)
+        if callable_obj:
+            args = (callable_obj,) + args
         return six.assertRaisesRegex(self, expected_exception,
-                re.escape(expected_message), callable_obj, *args, **kwargs)
+                re.escape(expected_message), *args, **kwargs)
 
     def assertFieldOutput(self, fieldclass, valid, invalid, field_args=None,
             field_kwargs=None, empty_value=''):

docs/releases/1.7.9.txt

@@ -8,3 +8,6 @@ Django 1.7.9 fixes several bugs in 1.7.8.
 
 * Prevented the loss of ``null``/``not null`` column properties during field
   renaming of MySQL databases (:ticket:`24817`).
+
+* Fixed ``SimpleTestCase.assertRaisesMessage()`` on Python 2.7.10
+  (:ticket:`24903`).

tests/test_utils/tests.py

@@ -605,6 +605,12 @@ def func1():
             raise ValueError("[.*x+]y?")
         self.assertRaisesMessage(ValueError, "[.*x+]y?", func1)
 
+    def test_callable_obj_param(self):
+        # callable_obj was a documented kwarg in older version of Django.
+        def func1():
+            raise ValueError("[.*x+]y?")
+        self.assertRaisesMessage(ValueError, "[.*x+]y?", callable_obj=func1)
+
 
 class AssertFieldOutputTests(SimpleTestCase):