title: Pyinstaller - "Fatal error ! Failed to execute script" when using multiprocessing.freeze_support
body: <p>I am using pyinstaller(v3.2.1) to build a --onefile windows exe. I am using multiprocessing within my python (v3.5.3) script. I have implemented the below mentioned workaround for windows.</p>
  
  <p><a href="https://github.com/pyinstaller/pyinstaller/wiki/Recipe-Multiprocessing" rel="noreferrer">Recipe Multiprocessing</a></p>
  
  <p>Logically, my python script does not span multiple process unless required / conditions are met and is working as expected. The issue I have is that, whenever multiple processes are involved, everything seems fine.
  But in case, if multiprocess is not involed, the below "Fatal: Could not execute the script" dialog box flashes for couple of seconds or more and then disappears still returning the expected results.</p>
  
  <p><a href="https://i.stack.imgur.com/zLUNf.png" rel="noreferrer"><img src="https://i.stack.imgur.com/zLUNf.png" alt="enter image description here"></a></p>
  
  <p>Is there anything I am missing that is causing the fatal error dialog to appear and disappear ? I suspect the <code>multiprocessing.freeze()</code> statement right after <code>if __name__ == __main__ :</code> might be causing the issue when new processes are not created! </p>