title: Django tests - patch object in all tests
body: <p>I need to create some kind of <code>MockMixin</code> for my tests. It should include mocks for everything that calls external sources.
  For example, each time I save model in admin panel I call some remote URLs. It would be good, to have that mocked and use like that:</p>
  
  <pre><code>class ExampleTestCase(MockedTestCase):
      # tests
  </code></pre>
  
  <p>So each time I save model in admin, for example in functional tests, this mock is applied instead of calling remote URLs.</p>
  
  <p>Is that actually possible? I'm able to do that for 1 particular test, that is not a problem. But it'd be more useful to have some global mock because I use it a lot.</p>