title: pytest AttributeError: "function object has no attribute" when referencing fixture in Python 3
body: <p>I have a model and a controller I'm trying to test:</p>
  
  <pre><code>class Model:
  
      def __init__(self):
          self.display = ""
  
      def set_display(self, display):
          self.display = display
  
  import pytest
  from model import Model
  from controller import Controller
  
  @pytest.fixture
  def model():
      return Model()
  
  @pytest.fixture
  def controller(model):
      return Controller(model)
  
  def test_clear_button(controller):
      controller.button_pressed("4")
      controller.button_pressed("2")
      controller.button_pressed("C")
      assert model.display == "0"
  </code></pre>
  
  <p>E       AttributeError: 'function' object has no attribute 'display'</p>
  
  <p>Above is the errors/failures I get every time I run the test.</p>
  
  <pre><code>class Controller:
  
      def __init__(self, model):
          self.model = model
  
      def button_pressed(self, button_label):
          pass
  </code></pre>