> In this case, the Powershell dependency fails on Windows 7 since it does not have the Invoke-WebRequest command (unless you've been installing all your updates).

Just to note, PowerShell must be updated *manually* (at least on Win7).  Plus you need to know what to update to get it. In this case, the Windows Management Framework:

https://www.microsoft.com/en-us/download/details.aspx?id=40855

I've installed this on my buildbot apparently concurrently with this conversation.  Personally, I'd lean toward recommending this update with Windows 7 machines as it stays closer to "naked" OS + Python checkout for building a new Python. (Although the latest merge kinda makes this a mute point).