tests/narrow-library.sh

debug: convert a few exceptions to bytes before wrapping in another error

Caught by pytype:

    File "/mnt/c/Users/Matt/hg/mercurial/debugcommands.py", line 2118, in debugmanifestfulltextcache: Function Abort.__init__ was called with the wrong arguments [wrong-arg-types]
             Expected: (self, message: Union[bytearray, bytes, memoryview], ...)
      Actually passed: (self, message: mercurial.error.LookupError, ...)
    File "/mnt/c/Users/Matt/hg/mercurial/debugcommands.py", line 2453, in debugobsolete: Function _bytestr.__init__ was called with the wrong arguments [wrong-arg-types]
             Expected: (self, ints: Iterable[int])
      Actually passed: (self, ints: ValueError)
      The following methods aren't implemented on ValueError:
      __iter__

Differential Revision: https://phab.mercurial-scm.org/D10174

cat >> $HGRCPATH <<EOF
[extensions]
narrow=
[ui]
ssh=$PYTHON "$RUNTESTDIR/dummyssh"
[experimental]
changegroup3 = True
EOF