title: python responses - Not all requests have been executed
body: <p>I'm trying test case to mock a api call and using python responses to mock the api call.</p>
  
  <p>Below is my mock, </p>
  
  <pre><code>with responses.RequestsMock() as rsps:
      url_re = re.compile(r'.*udemy.com/api-2.0/courses.*')           
      url_re = re.compile(r'https://www.udemy.com/api-2.0/courses')
      rsps.add(
          responses.GET, url_re,
          body=mocked_good_json, 
          status=200,
          content_type='application/json',
          match_querystring=True
      )
      courses = self.app.courses.get_all(page=1, page_size=2)         
      for course in courses:              
          self.assertTrue(isinstance(course, Course))
          self.assertTrue(hasattr(course, 'id'))
          self.assertTrue(hasattr(course, 'title'))           
          self.assertIsNotNone(course.id)        
  </code></pre>
  
  <p>When I execute this mock, I get this error - </p>
  
  <pre><code>AssertionError: Not all requests have been executed [(u'GET', 'https://www.udemy.com/api-2.0/courses/')]
  </code></pre>
  
  <p>When I remove the mock and directly call the api, it works fine.</p>
  
  <p>Any inputs on why my mock fails?</p>
  
  <p>Error message - </p>
  
  <pre><code>======================================================================
  FAIL: test_get_all_courses (tests.test_courses.TestApiCourses)
  ----------------------------------------------------------------------
  Traceback (most recent call last):
    File "/Users/rem/git/udemy/tests/test_courses.py", line 136, in test_get_all_courses
      courses = self.app.courses.get_all(page=1, page_size=2)
    File "/Users/rem/.virtualenvs/udemyapp/lib/python2.7/site-packages/responses.py", line 536, in __exit__
      self.stop(allow_assert=success)
    File "/Users/rem/.virtualenvs/udemyapp/lib/python2.7/site-packages/responses.py", line 620, in stop
      [(match.method, match.url) for match in not_called]
  AssertionError: Not all requests have been executed [(u'GET', 'https://www.udemy.com/api-2.0/courses/')]
  </code></pre>