Lesson of the day: Better don't abort bzr 'pushes'. You will get very interesting but confusing messages when you try to push next time:
ERROR: Lock was broken while still open: LockDir(sftp://bazaar.launchpad.net/%7Eubuntu-dev/aspectc%2B%2B/debian/.bzr/branch/lock) - check storage consistency!
UPDATE: ok, it seems to be fixable with this command:
bzr break-lock [LOCATION]