flushctl dies with usage statement

example invocation:

1. /usr/local/memcached/flushctl.py
   Usage: /usr/local/memcached/flushctl.py host:port start|stop
   or /usr/local/memcached/flushctl.py host:port set param value

Available params:
min_data_age - minimum data age before flushing data
queue_age_cap - maximum queue age before flushing data
max_txn_size - maximum number of items in a flusher transaction
Traceback (most recent call last):
File "/usr/local/memcached/flushctl.py", line 34, in ?
usage()
File "/usr/local/memcached/flushctl.py", line 26, in usage
exit(1)
TypeError: 'str' object is not callable

1. rpm -qv zmemcached
   zmemcached-1.5.3_rc1_12_gd793d31-1

CentOS 5.2 based on Rightscale AMI