title: Vapory Error: FileNotFoundError: [WinError 2] The system cannot find the file specified
body: <p>I ran vapory sample code in github, but it has errors.</p>
  
  <ul>
  <li><p>Code</p>
  
  <pre><code>from vapory import *
  
  camera = Camera( 'location', [0,2,-3], 'look_at', [0,1,2] )
  light = LightSource( [2,4,-3], 'color', [1,1,1] )
  sphere = Sphere( [0,1,2], 2, Texture( Pigment( 'color', [1,0,1] )))
  
  scene = Scene( camera, objects= [light, sphere])
  scene.render("purple_sphere.png", width=400, height=300)
  </code></pre></li>
  <li><p>Error Message</p>
  
  <pre><code> Traceback (most recent call last):
  File "C:\scene1.py", line 60, in &lt;module&gt;
  scene.render("scene1_vapory.png", width=640, height=480)
  File "C:\Users\User\Anaconda3\lib\site-packages\vapory\vapory.py", line 102, in render
  quality, antialiasing, remove_temp)
  File "C:\Users\User\Anaconda3\lib\site-packages\vapory\io.py", line 106, in render_povstring
  stdout=subprocess.PIPE)
  File "C:\Users\User\Anaconda3\lib\subprocess.py", line 775, in __init__
  restore_signals, start_new_session)
  File "C:\Users\User\Anaconda3\lib\subprocess.py", line 1178, in _execute_child
  startupinfo)
  FileNotFoundError: [WinError 2] The system cannot find the file specified
  </code></pre></li>
  </ul>