[MERGE] [BUG 363837] Catch OSError to make diff log debug message instead of passing win32 specific exception to stderr

[Martin Pool]

Martin Pool has voted tweak.
Status is now: Semi-approved
Comment:
That looks good, except that maybe you should include the exception too?

For details, see: 
http://bundlebuggy.aaronbentley.com/project/bzr/request/%3Cfuninal891aefr374gUYAxe124vaj_firegpg%40mail.gmail.com%3E
Project: Bazaar