Return the next open shard after shard_id

    CLI example::

        salt myminion boto_kinesis._get_next_open_shard existing_stream_details shard_id

def _get_next_open_shard(stream_details, shard_id):
    '''
    Return the next open shard after shard_id

    CLI example::

        salt myminion boto_kinesis._get_next_open_shard existing_stream_details shard_id
    '''
    found = False
    for shard in stream_details["OpenShards"]:
        current_shard_id = shard["ShardId"]
        if current_shard_id == shard_id:
            found = True
            continue
        if found:
            return current_shard_id