title: Error using FigureCanvasQTAgg in MatplotlibWidget pyqt5
body: <p>I would like to plot on my GUI with pyqt5 using matplotlib. I have created a class called MatplotlibWidget which create the figure and canvas of my plot. But I have a problem to generate my canvas with the FigureCanvasQTAgg function (which is a matplotlib function).</p>
  
  <p>Here the part of my code which is bugging:</p>
  
  <pre><code>import matplotlib.pyplot as plt
  from matplotlib.backends.backend_qt4agg import FigureCanvasQTAgg
  from matplotlib.figure import Figure
  
  #Some more code...not relevant
  
  class MatplotlibWidget(QWidget):
      def __init__(self):
          QWidget.__init__(self)
          self.fig = Figure()
          self.canvas = FigureCanvasQTAgg(self.fig) #line 86
          self.axis = self.fig.add_subplot(111)
  
          self.layoutVerticalTest = QVBoxLayout(self)
          self.layoutVerticalTest.addWidget(self.canvas)
  </code></pre>
  
  <p>I have this error : </p>
  
  <pre><code>File "/Users/AlexisTuil/Desktop/projet inno/sc_analysis/visualisation.py", line 86, in 
  __init__self.canvas = FigureCanvasQTAgg(self.fig)
  File "/usr/local/lib/python3.5/site packages/matplotlib/backends/backend_qt4agg.py", line 76, in     
  __init__FigureCanvasQT.__init__(self, figure)
  File "/usr/local/lib/python3.5/site-packages/matplotlib/backends/backend_qt4.py", line 71, in
  __init__QtWidgets.QWidget.__init__(self)
  TypeError: __init__() missing 1 required positional argument: 'figure'
  Abort trap: 6
  </code></pre>
  
  <p>I've searched on many forums but i couldn't find out a solution to my problem. I don't get it why there is a missing "positional argument". Please help me !</p>
  
  <p>I am on MacOS El Capitan with python3.5 64bit. I installed matplotlib with pip if it can help.</p>
  
  <p>Thanks guys :)</p>