On Windows 10 tests have undocumented dependency on USER environment variable

[david-pfx]

py.test.exe tests/unit

E RuntimeError: Attempting to use the value of the environment variable 'USER', which is not defined
c:\sw\python27\lib\site-packages\nupic\support\configuration_base.py:326: RuntimeError
---------------------------- Captured stderr call -----------------------------
ERR: Unable to create region classifier of type SDRClassifierRegion [C:\projects\nupic-core\src\nupic\engine\RegionImplFactory.cpp line 237]