'Returns the next Maintenance Window.
:return:  A dictionary containing maintenance window info (or None if
no maintenance windows are scheduled)
The dictionary contains 4 keys with values of type ``str``
- name: The name of the maintenance window
- description: Description of the maintenance window
- beginTime: RFC3339 Timestamp
- endTime: RFC3339 Timestamp
:rtype:   ``dict`` or ``None``'

def _get_next_maint(self):

    begin = None
    next_window = None
    if (not self.maintenance_windows):
        return None
    if (len(self.maintenance_windows) == 1):
        return self.maintenance_windows[0]
    for mw in self.maintenance_windows:
        begin_next = timestamp_to_datetime(mw['beginTime'])
        if ((not begin) or (begin_next < begin)):
            begin = begin_next
            next_window = mw
    return next_window
