Make some statistics on the run set.

def merge_webhooks_runset(runset):
    """Make some statistics on the run set.

    """
    min_started_at = min([w['started_at'] for w in runset])
    max_ended_at = max([w['ended_at'] for w in runset])
    ellapse = max_ended_at - min_started_at
    errors_count = sum(1 for w in runset if 'error' in w)
    total_count = len(runset)

    data = dict(
        ellapse=ellapse,
        errors_count=errors_count,
        total_count=total_count,
    )

    return data