code: def del_windows_env_var(key):
      
  
      if not isinstance(key, text_type):
          raise TypeError("%r not of type %r" % (key, text_type))
  
      status = winapi.SetEnvironmentVariableW(key, None)
      if status == 0:
          raise ctypes.WinError()
docs: Delete an env var.
  
      Raises:
          WindowsError