title: Opencv-Python error on when installing PyForms
body: <p>When I try to install PyForms by 'pip install pyforms', it threw an error:</p>
  
  <pre><code>https://files.pythonhosted.org/packages/47/9a/8d9364533ebcaa13621994a63dcc6a6051e27671ae5e1715dac4af18cac2/PyOpenGL-3.1.5-py3-none-any.whl
  ERROR: Could not find a version that satisfies the requirement
  opencv-python==3.4.5.20 (from pyforms-gui-&gt;pyforms) (from versions:
  3.4.8.29, 4.1.2.30) ERROR: No matching distribution found for opencv-python==3.4.5.20 (from pyforms-gui-&gt;pyforms)
  
  </code></pre>