title: Pytest skips test saying "asyncio not installed"
body: <p>When testing the following code</p>
  <pre><code>@pytest.mark.asynico
  async def test_handle_DATA(mocker):
      handle_mock = mocker.MagicMock()
      envelope_mock = mocker.MagicMock(mail_from=&quot;Test@From&quot;, rcpt_tos=[&quot;Test@To&quot;], content=b&quot;TestContent&quot;)
  
      result = SendToDictHandler.handle_DATA(handle_mock, &quot;TestServer&quot;, &quot;TestSession&quot;, envelope_mock)
  
      assert result == &quot;250 Message accepted for delivery&quot;
      assert email_core.testing_emails_dict == {
          &quot;Test@To&quot;: {
              &quot;from&quot;: &quot;Test@From&quot;,
              &quot;to&quot;: [&quot;Test@To&quot;],
              &quot;msg&quot;: &quot;TestContent&quot;,
          }
      }
  </code></pre>
  <p>The warning I get when running <code>pytest -vvv</code> in the projects environment:</p>
  <pre><code>PytestWarning: Coroutine functions are not natively supported and have been skipped.
  You need to install a suitable plugin for your async framework, for example:
   - pytest-asyncio
   - pytest-trio
   - pytest-tornasync
  warnings.warn(PytestWarning(msg.format(pyfuncitem.nodeid)))
  </code></pre>
  <p>I do have <code>pytest-asyncio</code> installed. I verified by running <code>pytest --trace-config</code> in my project's virtual environment</p>
  <pre><code>================== test session starts ======================
  platform win32 -- Python 3.7.1, pytest-4.4.1, py-1.8.0, pluggy-0.9.0
  using: pytest-4.4.1 pylib-1.8.0
  ...
  setuptools 
  registered plugins:
   - pytest-randomly-3.0.0 at \lib\site-packages\pytest_randomly.py
   - pytest-mock-1.10.2 at \lib\site-packages\pytest_mock.py
   - pytest-asyncio-0.10.0 at \lib\site-packages\pytest_asyncio\plugin.py
  
  active plugins:
   - pytest_mock         : \lib\site-packages\pytest_mock.py
   - asyncio             : \lib\site-packages\pytest_asyncio\plugin.py
  ...
  
  plugins: randomly-3.0.0, mock-1.10.2, asyncio-0.10.0
  </code></pre>