Summary:
Previously requesting remotefilelog file blobs from the server required write
access in order to write the blob to the cache. This changes it to not abort
entirely if the user doesn't have write access.
Test Plan:
cd tests
./run-tests.py --with-hg=/data/users/durham/hg/hg test-permissions.t
Also ran the test without the fix and verified it fails.
Reviewers: sid0, davidsp, pyd, dschleimer
Reviewed By: dschleimer
Differential Revision: https://phabricator.fb.com/D1145976
Task ID: 3601184
