Issue with fresh build on Windows: no module named "ng"

Created by: njlr

I have built the latest version (fca5b9aad... at the time of writing) with Ant on Windows. I installed the suggested dependencies using Chocolatey.

The build succeeds, but when I try to run Buck I get this error:

File "C:\Users\...\buck\third-party\nailgun\pynailgun\__init__.py", line 1, in <module>
  from ng import NailgunConnection, NailgunException
ModuleNotFoundError: No module named 'ng'

How (and where) should I install this module?