title: How to set background color to entire widget with stylesheet in PySide
body: <p>I am trying to set a background color of a widget, but it only applies to widget's children. The code below is a simple representation of the real app structure. I'd like testWidget to be entirely red, which is 100x100 pixel rectangle due to it's size, but for some reason only the button is red.</p>
  
  <pre><code>from PySide import QtGui
  
  
  class Widget(QtGui.QWidget):
  def __init__(self):
      QtGui.QWidget.__init__(self)
  
      mainLayout = QtGui.QVBoxLayout(self)
  
      testWidget = QtGui.QWidget()
      testWidget.setFixedSize(100,100)
  
      testWidget.setStyleSheet('background-color: red;')
      testLayout = QtGui.QVBoxLayout()
  
      testWidget.setLayout(testLayout)
  
  
      but = QtGui.QPushButton('TEST')
      but.setFixedSize(20,20)
      testLayout.addWidget(but)
  
      mainLayout.addWidget(testWidget)
  
  w = Widget()
  w.show()
  </code></pre>