NMAKE fatal error U1077 during rez-build

Running into a syntaxerror when trying to rez-build in windows

Command: rez-build --install (hello_world package)
Running: Windows 10, Rez 2.1.0

```
Error:
[100%] Generating py/python/hello_world.pyc
File "", line 1
'import
^
SyntaxError: EOL while scanning string literal
NMAKE : fatal error U1077: 'C:\Python27\python.EXE' : return code '0x1'
```

..and a couple of other nmake.exe errors return code 0x2

On my Linux boot everything runs perfectly. Not sure if its a rez issue specific to windows 10, nmake, vs or i just havent set my environment properly.

Edit: I should also mention that even after setting env variables i still had to replace 'cl' in the CMakeCache.txt in order to get it compiling.