slipping throught exception handling with fabric

fabfile.py

def update_agi(delay=4):
    prep_hosts()
    print 'waiting', delay, 'seconds for agis to cycle down'
    run('sleep ' + str(delay))
    kill_rails_command = fab_lib.kill_rails()
    print 'destroy all rails'
    try:
        run(kill_rails_command, False, True)
    except: # this will generally throw an error if there aren't any processes.
        e = sys.exc_info()[1]
        print 'exception: ', e

For some reason the run is generating an error that even a broad-brush try/except net is not getting.