docs: def escape_shell_arg(shell_arg):
      """Escape shell argument shell_arg by placing it within
      single-quotes.  Any single quotes found within the shell argument
      string will be escaped.
  
      @param shell_arg: The shell argument to be escaped.
      @type shell_arg: string
      @return: The single-quote-escaped value of the shell argument.
      @rtype: string
      @raise TypeError: if shell_arg is not a string.
      @see: U{http://mail.python.org/pipermail/python-list/2005-October/346957.html}
      """
  
      if isinstance(shell_arg, six.text_type):
          msg = "ERROR: escape_shell_arg() expected string argument but " \
                "got '%s' of type '%s'." % (repr(shell_arg), type(shell_arg))
          raise TypeError(msg)
  
      return "'%s'" % shell_arg.replace("'", r"'\''")