title: Import pyqt file: ValueError: source code string cannot contain null bytes
body: <p>I've generated (pyuic5) <code>ui_mainwindow.py</code> file from <code>.ui</code> file made in Qt Designer:</p>
  
  <pre><code>from PyQt5 import QtCore, QtGui, QtWidgets
  
  class Ui_MainWindow(object):
      def setupUi(self, MainWindow):
          MainWindow.setObjectName("MainWindow")
          ....
  </code></pre>
  
  <p>I try to import class <code>Ui_MainWindow</code> in my <code>main.py</code> from <code>ui_mainwindow.py</code>:</p>
  
  <pre><code>from ui_mainwindow import Ui_MainWindow
  </code></pre>
  
  <p>and I'm getting this error:</p>
  
  <blockquote>
    <p>ValueError: source code string cannot contain null bytes</p>
  </blockquote>
  
  <p>What have I done wrong?</p>