Try to get timezone using pytz or python-dateutil

    :param zone: timezone str
    :return: timezone tzinfo or None

def timezone(zone):
    """Try to get timezone using pytz or python-dateutil

    :param zone: timezone str
    :return: timezone tzinfo or None
    """
    try:
        import pytz
        return pytz.timezone(zone)
    except ImportError:
        pass
    try:
        from dateutil.tz import gettz
        return gettz(zone)
    except ImportError:
        return None