title: OpenCV: "[ WARN:0] terminating async callback" when attempting to take a picture
body: <p>I am trying to take a picture from the defualt carmera with python, to do this I am using openCV (<code>import cv2 as cv</code> from python shell). However, when I attempt to disable the camera it closes but with the error <code>[ WARN:0] terminating async callback</code>.</p>
  <p>This is code I am trying to run:</p>
  <pre class="lang-py prettyprint-override"><code>import cv2 as cv
  
  camera_port = 0
  camera = cv.VideoCapture(camera_port)
  return_value, image = camera.read()
  cv.imwrite(&quot;image.png&quot;, image)
  
  camera.release() # Error is here
  </code></pre>
  <p>The code outputs the desired result, it takes and saves an image, but I do not understand <em>why</em> the error message occurs or how to <em>remove</em> it</p>