test client puts different results in response.context when nested view is redirected with process_request vs process_response middleware

[Jay Cox]

When using the test client:

When a view calls another view and middleware causes the inner view to redirect - the contents of response.context will be different depending on if it was process_request, or process_response that initiated the redirect.

Test case for this error is in gitub:
​https://github.com/electricjay/django/tree/test_client_nested_testcase

This problem was discovered when creating the pull request ​https://github.com/django/django/pull/4574 for ticket #24696

[Jay Cox]

I have tracked the cause down and I no longer think this is a bug with the test client.

When the redirect happens in process_response a 404 response is created using a template before process_response is run. Thus the test client is legitimately(?) adding the context from the 404 response to the context of the response that is ultimately returned.

I suggest only modifying the test test_client_regress.tests.ContextTests.test_nested_requests to not trigger the common middleware.