alarm-list crashes if no time_constraints

If the client is run against a ceilometer service that doesn't return time_constraint data, the client simply reports "time_constraints".
This is somewhat cryptic...

The stack trace is as follows:
Traceback (most recent call last):
File "/Users/martinpaulo/.virtualenvs/osclt/bin/ceilometer", line 10, in <module> sys.exit(main())
File "/Users/martinpaulo/.virtualenvs/osclt/lib/python2.7/site-packages/ceilometerclient/shell.py", line 335, in main CeilometerShell().main(args)
File "/Users/martinpaulo/.virtualenvs/osclt/lib/python2.7/site-packages/ceilometerclient/shell.py", line 289, in main args.func(client, args)
File "/Users/martinpaulo/.virtualenvs/osclt/lib/python2.7/site-packages/ceilometerclient/v2/shell.py", line 284, in do_alarm_list 'time_constraints': time_constraints_formatter}, sortby=0)
File "/Users/martinpaulo/.virtualenvs/osclt/lib/python2.7/site-packages/ceilometerclient/common/utils.py", line 65, in print_list sortby_index=sortby)
File "/Users/martinpaulo/.virtualenvs/osclt/lib/python2.7/site-packages/ceilometerclient/openstack/common/cliutils.py", line 154, in print_list row.append(formatters[field](o))
File "/Users/martinpaulo/.virtualenvs/osclt/lib/python2.7/site-packages/ceilometerclient/v2/shell.py", line 229, in time_constraints_formatter return _display_time_constraints(alarm.time_constraints)
File "/Users/martinpaulo/.virtualenvs/osclt/lib/python2.7/site-packages/ceilometerclient/v2/alarms.py", line 52, in __getattr__ return super(Alarm, self).__getattr__(k)
File "/Users/martinpaulo/.virtualenvs/osclt/lib/python2.7/site-packages/ceilometerclient/openstack/common/apiclient/base.py", line 463, in __getattr__ raise AttributeError(k)
AttributeError: time_constraints

The fix I applied to tide me over was to simply alter the time_constraints_formatter method in shell.py (line 229) to read as follows:

def time_constraints_formatter(alarm):
    if hasattr(alarm, 'time_constraints'):
        return _display_time_constraints(alarm.time_constraints)
    return 'None'

I'm not submitting a patch because I'm not sure that this is the behavior that is actually desired, and also because I don't have time to properly write a test :(