title: Python "responses" mock - unable to call one URL multiple times
body: <p>I'm using python <code>responses</code> module to mock API response in my tests. The problem is that after the url is registered <code>responses.add()</code> it can be called <strong>only once</strong> with <code>requests.get()</code>, subsequent calls for the same URL raise an exception.</p>
  <pre class="lang-py prettyprint-override"><code>import requests
  import responses
  
  URL = 'http://localhost/abcd'
  
  # Test method
  @responses.activate
  def get_url(url):
    return requests.get(url)
  
  # Set up URL mock
  responses.add(responses.GET, URL, body=&quot;A B C D&quot;)
  </code></pre>
  <p>Now the first call works:</p>
  <pre class="lang-py prettyprint-override"><code>&gt;&gt;&gt; print(get_url(URL))   # &lt;Response [200]&gt;
  </code></pre>
  <p>However the same call again fails:</p>
  <pre class="lang-py prettyprint-override"><code>&gt;&gt;&gt; print(get_url(URL))
  
  Traceback (most recent call last):
    File &quot;test-responses.py&quot;, line 19, in &lt;module&gt;
      print(get_url(URL))
    File &quot;&lt;string&gt;&quot;, line 3, in wrapper
    File &quot;test-responses.py&quot;, line 10, in get_url
      return requests.get(url)
    File &quot;.../site-packages/requests/api.py&quot;, line 75, in get
      return request('get', url, params=params, **kwargs)
    File &quot;.../site-packages/requests/api.py&quot;, line 60, in request
      return session.request(method=method, url=url, **kwargs)
    File &quot;.../site-packages/requests/sessions.py&quot;, line 533, in request
      resp = self.send(prep, **send_kwargs)
    File &quot;.../site-packages/requests/sessions.py&quot;, line 646, in send
      r = adapter.send(request, **kwargs)
    File &quot;.../site-packages/responses.py&quot;, line 674, in unbound_on_send
      return self._on_request(adapter, request, *a, **kwargs)
    File &quot;.../site-packages/responses.py&quot;, line 654, in _on_request
      raise response
  requests.exceptions.ConnectionError: Connection refused by Responses - the call doesn't match any registered mock.
  
  Request: 
  - GET http://localhost/abcd
  
  Available matches:
  
  &gt;&gt;&gt;
  </code></pre>
  <p>Is there any way to make the mock URLs permanent and call them as many times as the tests need?</p>