Merge lp://staging/~facundo/ubuntuone-client/lr-udf-not-found into lp://staging/ubuntuone-client

Hmm. Not sure that adding an os.access check beforehand covers it. What happens if someone deletes/chmods/etc the directory between the call to os.access but before _add_watches_to_udf_ancestors completes? Seems like it would hit the same loop as before.

(This might happen in practice if e.g. the user were doing bulk permissions changes/moves/deletions while syncdaemon just happened to be in this part of the code.)

(It seems like the correct fix would be to make _add_watches_to_udf_ancestors robustly raise an exception if the directory is gone or disappears out from under it, then catch that exception to do the unsubscribe.)

Tim: Thanks for your comment!

I refactored the check, and now I do the following:

- Start to adding watches to the ancestors (if some of the ancestors is not there, the whole subtree was moved or deleted, so I revert stuff (see below))

- When finished with ancestors, check the UDF itself (if not there, also revert stuff).

"revert stuff" means removing the added watches (not the watches of all ancestors, but only the added ones, because ancestors can be shared between UDFs) and unsubscribing the UDF.

Could you please review it again?

Thank you very much!

All tests pass, and Tim's comment was addressed, so approving

Much better. I'd suggest calling the one function revert_watches rather than restore_watches (the latter implying that watches are being put back rather than removed).