title: Cannot Install dlib and OpenCV together in Anaconda for required python-versions' mismatch
body: <p>I am trying to develop a system that requires OpenCV and dlib to be installed in anaconda to work with. I tried a lot to install dlib package in latest anaconda (Anaconda3-2019.03-Windows-x86_64) distribution. But it says to downgrade the python version. Again I also found the dlib package does not still support python3.7. See here the available versions:</p>
  
  <pre><code>https://pypi.org/simple/dlib/
  </code></pre>
  
  <p>Than I created a virtual environment having python3.6. But I faced another type of error. It cannot play video file (mp4). But it works fine if the video is taken from webcam. It shows the following error:</p>
  
  <pre><code>gray=cv.cvtColor(frame,cv.COLOR_BGR2GRAY) error: ..\..\..\modules\imgproc\src\color.cpp:3739: error: (-215) scn == 3 || scn == 4 in function cv::cvtColor
  </code></pre>
  
  <p>As I found this error occurs when it doesn't find any video file. But in my case there is no reason of not finding a video file. I tried both by using video file name (keeping it in the same folder) and full path as well. It behaves the same.</p>
  
  <p>Than I installed Anaconda3 (5.0.1) which comes with python3.6 which should work fine but I failed to install OpenCV using command:</p>
  
  <pre><code>conda install -c conda-forge OpenCV
  </code></pre>
  
  <p>It says:</p>
  
  <pre><code>CondaError: Cannot link a source that does not exist. C:\Users\Username\Anaconda3\Scripts\conda.exeRunning `conda clean --packages` may resolve your problem.
  </code></pre>
  
  <p>It throws the same error even if I try to install OpenCV after cleaning conda packeges.</p>
  
  <p>With which versions of these navigator, python, OpenCV and dlib I can make a stable working environment for my work and how?</p>
  
  <p>Summarizing what I want:</p>
  
  <ol>
  <li>A stable anaconda installation</li>
  <li>Can work with dlib and OpenCV libraries</li>
  <li>No problem in working with video files. No matter it comes   from
  webcam or other saved video.</li>
  </ol>
  
  <p>Please help me :( </p>