pytest-watcher triggering issue new_snapshot.path_for_inode(ref_stat_info.st_ino)) AttributeError: 'DirectorySnapshot' object has no attribute 'path_for_inode'

[scheung38]

MacOSX 10.14.2
Python 3.7.2

`$ ptw --onpass "say passed" --onfail "say failed"

new_snapshot.path_for_inode(ref_stat_info.st_ino))

AttributeError: 'DirectorySnapshot' object has no attribute 'path_for_inode'

`

only works on 2 code changes, whether my test ran from failed to passed, or passed to failed, or passed to passed. Haven't checked any other combinations, but why does the watcher stops running after two events any more changes in my source and test code, nothing happens until I CTRL-C to restart??