'Constructs an :class:`Arrow <arrow.arrow.Arrow>` object from a date string and format,
in the style of ``datetime.strptime``.
:param date_str: the date string.
:param fmt: the format string.
:param tzinfo: (optional) an optional ``tzinfo``'

@classmethod
def strptime(cls, date_str, fmt, tzinfo=None):

    dt = datetime.strptime(date_str, fmt)
    tzinfo = (tzinfo or dt.tzinfo)
    return cls(dt.year, dt.month, dt.day, dt.hour, dt.minute, dt.second, dt.microsecond, tzinfo)
