slipping throught exception handling with fabric

fabfile.py

import time
from fabric.api import puts

def update_agi(delay=4):
    prep_hosts()
    puts('waiting %s seconds for agis to cycle down' % delay)
    time.sleep(delay)
    fab_lib.kill_rails()

# where ever this is defined
def kill_rails():
    # generate command string
    puts('destroy all rails')
    with settings(warn_only=True):
        run(kill_rails_command, shell=False, pty=True)