unit test flaky due to fs event -

[ecyrbe]

I get these on my PR, that do not seem to be related to code i pushed #4202 :

OK     fsEventsBasic (2.00ms)
##[error]thread '<unnamed>' panicked at 'fs events error: SendError(Ok(FsEvent { kind: "modify", paths: ["/tmp/8259b2ca/file2.txt"] }))', src/libcore/result.rs:1188:5

[ecyrbe]

@bartlomieju any idea why this fs event test panics ?

[bartlomieju]

Most likely because FsWatcher doesn't stop watching after it's closed an tries to push new notification on a channel that has been closed.

CC @ry you might want to call 'unwatch' when closing watcher resource