RuntimeError: Attempting to use the value of the environment variable 'USER', which is not defined

[chhenning]

Traceback (most recent call last):
  File "htmpredictionmodel_classifier_helper_test.py", line 151, in setUp
    self.helper = HTMPredictionModelClassifierHelper(Mock(spec=HTMPredictionModel))
  File "D:\nupic\src\python\python3\nupic\frameworks\opf\htm_prediction_model_classifier_helper.py", line 74, in __init__
    'nupic.model.temporalAnomaly.wait_records'))
  File "D:\nupic\src\python\python3\nupic\support\configuration_base.py", line 157, in get
    return cls.getString(prop)
  File "D:\nupic\src\python\python3\nupic\support\configuration_base.py", line 84, in getString
    cls._readStdConfigFiles()
  File "D:\nupic\src\python\python3\nupic\support\configuration_custom.py", line 148, in _readStdConfigFiles
    super(Configuration, cls)._readStdConfigFiles()
  File "D:\nupic\src\python\python3\nupic\support\configuration_base.py", line 409, in _readStdConfigFiles
    cls.readConfigFile(DEFAULT_CONFIG)
  File "D:\nupic\src\python\python3\nupic\support\configuration_base.py", line 207, in readConfigFile
    properties = cls._readConfigFile(filename, path)
  File "D:\nupic\src\python\python3\nupic\support\configuration_base.py", line 325, in _readConfigFile
    " variable %r, which is not defined" % (varname))
RuntimeError: Attempting to use the value of the environment variable 'USER', which is not defined