Get logs for a specific log group

def log_entries_from_group(session, group_name, start, end):
    '''Get logs for a specific log group'''
    logs = session.client('logs')
    log.info("Fetching logs from group: %s" % group_name)
    try:
        logs.describe_log_groups(logGroupNamePrefix=group_name)
    except ClientError as e:
        if e.response['Error']['Code'] == 'ResourceNotFoundException':
            return
        raise
    try:
        log_streams = logs.describe_log_streams(
            logGroupName=group_name,
            orderBy="LastEventTime",
            limit=3,
            descending=True,
        )
    except ClientError as e:
        if e.response['Error']['Code'] == 'ResourceNotFoundException':
            return
        raise
    start = _timestamp_from_string(start)
    end = _timestamp_from_string(end)
    for s in reversed(log_streams['logStreams']):
        result = logs.get_log_events(
            logGroupName=group_name,
            logStreamName=s['logStreamName'],
            startTime=start,
            endTime=end,
        )
        for e in result['events']:
            yield e