newforms-admin: Fixed failing test by changing never_cache header to handle views that don't return a response object. The test traceback was:

======================================================================
ERROR: Test add view restricts access and actually adds items.
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Traceback (most recent call last):
  File ".../tests/regressiontests/admin_views/tests.py", line 178, in testAddView
    post = self.client.post('/test_admin/admin/admin_views/article/add/', self.super_login)
  File ".../django/test/client.py", line 265, in post
    return self.request(**r)
  File ".../django/core/handlers/base.py", line 82, in get_response
    response = callback(request, *callback_args, **callback_kwargs)
  File ".../django/contrib/admin/sites.py", line 113, in root
    response = self.login(request)
  File ".../django/views/decorators/cache.py", line 45, in _wrapped_view_func
    add_never_cache_headers(response)
  File ".../django/utils/cache.py", line 118, in add_never_cache_headers
    patch_response_headers(response, cache_timeout=-1)
  File ".../django/utils/cache.py", line 106, in patch_response_headers
    if not response.has_header('ETag'):
AttributeError: 'NoneType' object has no attribute 'has_header'


git-svn-id: http://code.djangoproject.com/svn/django/branches/newforms-admin@7824 bcc190cf-cafb-0310-a4f2-bffc1f526a37

django/views/decorators/cache.py

@@ -42,6 +42,9 @@ def never_cache(view_func):
     """
     def _wrapped_view_func(request, *args, **kwargs):
         response = view_func(request, *args, **kwargs)
-        add_never_cache_headers(response)
+        # Although rare, it is possible for a view to return None (e.g. the
+        # django.contrib.admin.sites.AdminSite.login view in one corner-case)
+        if response:
+            add_never_cache_headers(response)
         return response
     return wraps(view_func)(_wrapped_view_func)