tags: silence hgtagsfnodes reading failures
tryread() doesn't handle "is a directory" errors and presumably
others. We might not want to globally swallow such tryread errors, so
we replace with our own try/except handling.
An upcoming test will use directories as a portable stand-in for
various bizarre circumstances that cache read/write code should be
robust to.
#require docutils gettext
$ $TESTDIR/check-gendoc ru
checking for parse errors