manifest-cache: ignore IOError while writing If the wcache directory is non writable for some reason (eg: belong to root). Trying to write to it currently crash Mercurial. Instead we ignore the error and skip writing that cache. We should probably improve the user experience of multiple users interacting with the same repository. However this is not an adventure for stable. Differential Revision: https://phab.mercurial-scm.org/D8512