argparse class to properly indent subparser help

proper_indent_parser.py

class ProperIndentParser(argparse.ArgumentParser):
    """Use formatter_class that properly indents help in subparsers"""

    def __init__(self, *args, **kwargs):
        formatter_class = lambda prog: ProperIndentFormatter(prog)
        argparse.ArgumentParser.__init__(
            self, *args, **kwargs, formatter_class=formatter_class)


class ProperIndentFormatter(argparse.HelpFormatter):
    """Corrected _max_action_length for the indenting of subactions

    Source: https://stackoverflow.com/a/32891625/2868017
    """

    def add_argument(self, action):
        if action.help is not argparse.SUPPRESS:
            # find all invocations
            get_invocation = self._format_action_invocation
            invocations = [get_invocation(action)]
            current_indent = self._current_indent
            for subaction in self._iter_indented_subactions(action):
                # compensate for the indent that will be added
                indent_chg = self._current_indent - current_indent
                added_indent = "x"*indent_chg
                invocations.append(added_indent + get_invocation(subaction))

            # update the maximum item length
            invocation_length = max([len(s) for s in invocations])
            action_length = invocation_length + self._current_indent
            self._action_max_length = max(
                self._action_max_length, action_length)

            # add the item to the list
            self._add_item(self._format_action, [action])