import six
import pytz


def make_aware(dt, tz=None):
    """
    Convert naive datetime object to tz-aware
    """
    if tz:
        if isinstance(tz, six.string_types):
            tz = pytz.timezone(tz)
    else:
        tz = pytz.utc
    if dt.tzinfo:
        return dt.astimezone(dt.tzinfo)
    else:
        return tz.localize(dt)