obscache: ignore permission and OS errors when writing
In practice we always update this cache along side a new transaction, with lock
taken so permission issues should not happens. However, staying on the safe side
is better. Errors during Cache update should not block Mercurial operations.
#require test-repo pyflakes
Copied from Mercurial core (60ee2593a270)
$ cd "`dirname "$TESTDIR"`"
run pyflakes on all tracked files ending in .py or without a file ending
(skipping binary file random-seed)
$ hg locate 'set:(**.py or grep("^#!.*python")) - removed()' 2>/dev/null \
> | xargs pyflakes 2>/dev/null