def validate_list(integer_list):
    """
    Ensure that the user-supplied input is a list of integers, or a list of strings
    that can be parsed as integers.
    """
    if not integer_list:
        raise Exception(
            'No bugs to migrate! Call `migrate` with a list of bug ids.')
    if not isinstance(integer_list, list):
        raise Exception('Expected a list of integers. Instead recieved a(n) {}'
            .format(type(integer_list)))
        for i in integer_list:
            try:
                int(i)
            except ValueError:
                raise Exception(
                    '{} is not able to be parsed as an integer, and is therefore an invalid bug id.'
                    .format(i))
