presenceservice.py has broken string formatting syntax

[walter]

There are several places throughout the code that use a comma instead of a % so that the format of error messages and log messages break, e.g.:

if self._activity_cache is not None:

raise ValueError('Activity %s is already tracked',

activity.get_id())

should be:

if self._activity_cache is not None:

raise ValueError('Activity %s is already tracked' % \

activity.get_id())

I'll attach a patch.