def import_moderator(app):
    """
    Import moderator module and register all models it contains with moderation
    """
    from importlib import import_module
    import imp
    try:
        app_path = import_module(app).__path__
    except AttributeError:
        return None
    try:
        imp.find_module('moderator', app_path)
    except ImportError:
        return None
    module = import_module('%s.moderator' % app)
    return module
