title: pytest fixture - get value and avoid error "Fixture 'X' called directly"
body: <p>I have updated pytest to 4.3.0 and now I need to rework test code since calling fixtures directly is deprecated. </p>
  
  <p>I have an issue with fixtures used in an unittest.TestCase, how do I get the value returned from the fixture and not a reference to the function itself ?</p>
  
  <p>Example :</p>
  
  <pre><code>@pytest.fixture
  def test_value():
      return 1
  
  @pytest.mark.usefixtures("test_value")
  class test_class(unittest.TestCase):
      def test_simple_in_class(self):
          print(test_value)    # prints the function reference and not the value
          print(test_value())  # fails with Fixtures are not meant to be called directly
  
  def test_simple(test_value):
      print(test_value)  # prints 1
  </code></pre>
  
  <p>How can I get test_value in the test_simple_in_class() method ?</p>