title: Adding into Path var while silent installation of Python - possible bug?
body: <p>I need to passively install Python in my applications package installation so i use the following:</p>
  
  <pre><code>python-3.5.4-amd64.exe /passive PrependPath=1
  </code></pre>
  
  <p>according this: <a href="https://docs.python.org/3.6/using/windows.html#installing-without-ui" rel="nofollow noreferrer">3.1.4. Installing Without UI</a> I use the PrependPath parameter which should add paths into Path in Windows environment variables.</p>
  
  <p>But it seems not to work. The variables does not take any changes.</p>
  
  <p>If i start installation manually and select or deselect checkbox with add into Paths then everything works.</p>
  
  <p>Works same with clear installation also on modify current installation. Unfortunately i do not have other PC with Win 10 Pro to test it.</p>
  
  <p>I have also tried it with Python 3.6.3 with same results.</p>
  
  <p><strong>EDIT:</strong></p>
  
  <p>Also tried with PowerShell <code>Start-Process python-3.5.4-amd64.exe -ArgumentList /passive , PretendPath=1</code> with same results.</p>
  
  <p>Also tested on several PCs with Windows 10, same results, so the problem is not just on single PC</p>
  
  <p><strong>EDIT:</strong>
  Of cource all attempts were run as administrator.</p>