fix backtrace printed when cannot get lock.
change lock error handling code so exceptions have useful info and
exception handling in one place.
add test case for when cannot get lock.
changeset: 0:0acdaf898367
tag: tip
user: test
date: Mon Jan 12 13:46:40 1970 +0000
summary: test
changeset: 1:c5c60883086f
tag: tip
user: test
date: Mon Jan 12 13:46:40 1970 +0000
summary: Added tag bleah for changeset 0acdaf8983679e0aac16e811534eb49d7ee1f2b4
changeset: 0:0acdaf898367
tag: bleah
user: test
date: Mon Jan 12 13:46:40 1970 +0000
summary: test
abort: working copy of .hgtags is changed (please commit .hgtags manually)
failed
use of 'hg tag NAME [REV]' is deprecated, please use 'hg tag [-r REV] NAME' instead
abort: use only one form to specify the revision
failed
use of 'hg tag NAME [REV]' is deprecated, please use 'hg tag [-r REV] NAME' instead
0acdaf8983679e0aac16e811534eb49d7ee1f2b4 bleah
0acdaf8983679e0aac16e811534eb49d7ee1f2b4 bleah0
c5c60883086f5526bd3e36814b94a73a4e75e172 bleah1
abort: '\n' cannot be used in a tag name
abort: ':' cannot be used in a tag name