title: 'Choco install python' fails on AppVeyor with 1603
body: <p>I have a PowerShell build script that installs Python from Chocolatey:</p>
  
  <pre><code>choco install python -y
  </code></pre>
  
  <p>But even though it works on local machines, running it on AppVeyor will fail half-silently:</p>
  
  <pre><code>[00:01:07] Chocolatey v0.10.3
  [00:01:07] Installing the following packages:
  [00:01:07] python
  [00:01:07] By installing you accept licenses for the packages.
  [00:01:08]
  [00:01:08] python3 v3.6.0 [Approved]
  [00:01:08] python3 package files install completed. Performing other installation steps.
  [00:01:09] Downloading python3 64 bit
  [00:01:09]   from 'https://www.python.org/ftp/python/3.6.0/python-3.6.0-amd64.exe'
  [00:01:09]
  [00:01:09] Progress: 0% - Saving 26.78 KB of 30.05 MB (27420/31505640)
  ... *download info*
  [00:01:10] Progress: 100% - Completed download of C:\Users\appveyor\AppData\Local\Temp\chocolatey\python3\3.6.0\python-3.6.0-amd64.exe (30.05 MB).
  [00:01:10] Download of python-3.6.0-amd64.exe (30.05 MB) completed.
  [00:01:13] Hashes match.
  [00:01:13] Installing python3...
  [00:01:51] ERROR: Running ["C:\Users\appveyor\AppData\Local\Temp\chocolatey\python3\3.6.0\python-3.6.0-amd64.exe" /quiet InstallAllUsers=1 PrependPath=1 TargetDir="C:\Python36" ] was not successful. Exit code was '1603'. See log for possible error messages.
  [00:01:52] The install of python3 was NOT successful.
  [00:01:52] Error while running 'C:\ProgramData\chocolatey\lib\python3\tools\chocolateyInstall.ps1'.
  [00:01:52]  See log for details.
  [00:01:54]
  [00:01:54] python v3.6.0 [Approved]
  [00:01:54] python package files install completed. Performing other installation steps.
  [00:01:54]  The install of python was successful.
  [00:01:54]   Software install location not explicitly set, could be in package or
  [00:01:54]   default install location if installer.
  [00:01:54]
  [00:01:54] Chocolatey installed 1/2 packages. 1 packages failed.
  [00:01:54]  See the log for details (C:\ProgramData\chocolatey\logs\chocolatey.log).
  [00:01:54]
  [00:01:54] Failures
  [00:01:54]  - python3 (exited 1603) - Error while running 'C:\ProgramData\chocolatey\lib\python3\tools\chocolateyInstall.ps1'.
  [00:01:54]  See log for details.
  [00:01:54] 2016-03-28 11:31:39,117 [DEBUG] - Configured chocolatey.infrastructure.logging.log4net.config.xml from assembly choco, Version=0.9.9.12, Culture=neutral, PublicKeyToken=79d02ea9cad655eb
  ... *unrelated*
  </code></pre>
  
  <p>The log doesn't tell me anything useful. Is this a bug from Chocolatey, a problem with the package or, hopefully, something wrong with the VM environment?</p>