def _nonbreaking_spaces(match_obj):
    """
    Make spaces visible in HTML by replacing all `` `` with ``&nbsp;``

    Call with a ``re`` match object.  Retain group 1, replace group 2
    with nonbreaking speaces.
    """
    spaces = '&nbsp;' * len(match_obj.group(2))
    return f'{match_obj.group(1)}{spaces}'
