Warnings on excluded files

[shacker]

My exclusion regexes are working fine, but I'm getting lots of warnings like:

WARNING: /path/to/file could not be accessed (no permissions to read?)

That's probably because I ran the script without sudo and some dirs are off-limits, but if I've excluded /path/to, it shouldn't even be looking at that path, so why the warning?

[mjurbanski-reef]

Currently, exclusion happens after iteration of files, so it is indeed suboptimal.

This will likely also cause b2 CLI to return status code 1 (fail) even if inaccessible are skipped, which makes it not only annoying but a full fledged bug that has to be fixed.

[titus8]

This inspired me to add filtering the sys.stderr replacement I pass to SyncReport.

[shacker]

Thanks for the fix!