the problem was that the borg process removed its own shared lock when upgrading it to an exclusive lock.
this is fine if we get the exclusive lock, but if we don't, we must re-add our shared lock.
this fixes the KeyError in locking.py:217
subclasses of "Error": do not show traceback
(this is used when a failure is expected and has rather trivial reasons and usually
does not need debugging)
subclasses of "ErrorWithTraceback": show a traceback
(this is for severe and rather unexpected stuff, like consistency / corruption issues
or stuff that might need debugging)
I reviewed all the Error subclasses whether they fit into the one or other class.
Also: fixed docstring typo, docstring formatting
there were 2 issues:
lock used another pid and tid than release because daemonize() made it different processes/threads.
solved by just determining PID only once and not using TID any more.
the other issue was that the repo needed and explicit closing.
