title: import cv2 error on django ImportError: libGL.so.1
body: <p>i'm working on a django project and i need to use the webcam. i've tried to install opencv-python with pip but python give me back the error <code>ImportError: libGL.so.1: cannot open shared object file: No such file or directory</code>.
  i've tried to install libGL.so.1 inside Dockerfile:</p>
  <pre><code>RUN apt-get update
  RUN apt-get install libgl1 -y  
  </code></pre>
  <p>but I haven't solved my problem.</p>