message: drake: beware that os is actually _OS
diff: @@ -39,8 +39,8 @@ from drake.utils import property_memoize, pretty_listing
  # The default timeout value for shell commands, in seconds.
  TIMEOUT = int(_OS.getenv('DRAKE_TIMEOUT', '3600'))
  -PRETTY = 'DRAKE_PRETTY' in os.environ
  -PROFILE = 'DRAKE_PROFILE' in os.environ
  +PRETTY = 'DRAKE_PRETTY' in _OS.environ
  +PROFILE = 'DRAKE_PROFILE' in _OS.environ
  def _scheduled():
  @@ -2008,7 +2008,7 @@ class Builder:
  else:
  stdout = None
  if env is not None:
  - os_env = os.environ.copy()
  + os_env = _OS.environ.copy()
  os_env.update(env)
  my_env = os_env
  else:
  