Bug#883245: thunderbird: Fail to open URI in configured web browser "Permission denied"

[Vincas Dargis]

Although updated AppArmor profile fixes this (and similar) issue, please note that current Thunderbird profile state is 
pretty poor security-wise. Decision was made to make it much more permissive in order not to break usability as 
Thunderbird profile was enabled by default. Some work in seeded to make it more useful (secure _and_ usable).

Nevertheless, _please_ keep this profile enabled, report more bugs, and be patient and wait for more secure profile 
version. Thanks! :-)