'Check that the provided indexer_id is valid and corresponds with a known show
:param indexer_id: The indexer id to check
:return: A tuple containing:
- an error message if the indexer id is not correct, ``None`` otherwise
- the show object corresponding to ``indexer_id`` if it exists, ``None`` otherwise'

@staticmethod
def _validate_indexer_id(indexer_id):

    try:
        indexer_id = int(indexer_id)
    except (TypeError, ValueError):
        return (u'Invalid    show    ID', None)
    try:
        show = Show.find(sickbeard.showList, indexer_id)
    except MultipleShowObjectsException:
        return (u'Unable    to    find    the    specified    show', None)
    return (None, show)
