Sys error on file reload

[ncannasse]

As discussed here:
https://community.heaps.io/t/questions-regarding-live-update/65
Sometimes file change detection will trigger a sys error when trying to read the file.

I'm not sure about the best way to deal with this. We're already trying to open the file with "append" mode just before calling watchCallback in LocalFileSystem.checkFiles. Maybe we should hold the lock during the whole callback handling.

[ncannasse]

@D0pu I think I might have undo some of your changes wrt this with my latest convert patch.

Maybe one way to do it would be (on watch event) to try/catch any error, then if there is an error, retry after 1s - without try/catch this time so we can get the eventual real error. Have to be careful if multiple watch events are triggered in meanwhile