reopens a closed poll.

def reopen(args):
    """reopens a closed poll."""
    if not args.isadmin:
        return "Nope, not gonna do it."
    msg = args.msg.split()
    if not msg:
        return "Syntax: !poll reopen <pollnum>"
    if not msg[0].isdigit():
        return "Not a valid positve integer."
    pid = int(msg[0])
    poll = get_open_poll(args.session, pid)
    if poll is None:
        return "That poll doesn't exist or has been deleted!"
    poll.active = 1
    return "Poll %d reopened!" % pid