code: def putenv(key, value):
      
  
      key = path2fsn(key)
      value = path2fsn(value)
  
      if is_win and PY2:
          try:
              set_windows_env_var(key, value)
          except WindowsError:
              # py3 + win fails here
              raise ValueError
      else:
          try:
              os.putenv(key, value)
          except OSError:
              # win + py3 raise here for invalid keys which is probably a bug.
              # ValueError seems better
              raise ValueError
docs: Like `os.putenv` but takes unicode under Windows + Python 2
  
      Args:
          key (pathlike): The env var to get
          value (pathlike): The value to set
      Raises:
          ValueError