docs: def credentials(login=None):
      """
      Find user credentials. We should have parsed the command line for a ``--login`` option.
      We will try to find credentials in environment variables.
      We will ask user if we cannot find any in arguments nor environment
      """
      if not login:
          login = environ.get("PROF_LOGIN")
      password = environ.get("PROF_PASSWORD")
      if not login:
          try:
              login = input("login? ")
              print("\t\tDon't get prompted everytime. Store your login in the ``~/.profrc`` config file")
          except KeyboardInterrupt:
              exit(0)
      if not password:
          try:
              password = getpass.getpass("pass for {0} ? ".format(login))
          except KeyboardInterrupt:
              exit(0)
      return (login, password)