Fix :class:`argparse.ArgumentParser` with the *formatter_class* argument.
Fix TypeError when *formatter_class* is a custom subclass of
:class:`!HelpFormatter`.
Fix TypeError when *formatter_class* is not a subclass of
:class:`!HelpFormatter` and non-standard *prefix_char* is used.
Fix support of colorizing when *formatter_class* is not a subclass of
:class:`!HelpFormatter`.
