Jenkins disk space checker

#!/usr/bin/env python3.6

import jenkins
import sys

def main(username, password):
    server = jenkins.Jenkins('http://akaitech.com:5000'
                             , username=username
                             , password=password)

    for node in server.get_nodes():
        if node['offline']:
            print("Node %s: is offline" % node['name'])
        elif node['name'] != 'master':
            node_info = server.get_node_info(node['name'])
            try:
                free_space = node_info['monitorData'] \
                                      ['hudson.node_monitors.DiskSpaceMonitor'] \
                                      ['size']

                free_space_gb = int(free_space / (1024 ** 3))
                print("Node %s: has free space %sGB" % (node['name'], free_space_gb))
            except KeyError:
                print("Node %s: could not get free space")

def usage():
    print("Usage:")
    print("%s <username> <password>" % sys.argv[0])
    sys.exit(1)

if __name__ == "__main__":
    if len(sys.argv) != 3:
        usage()

    main(sys.argv[1], sys.argv[2])