tests/narrow-library.sh

remotefilelog: fix some bytes/str portability issues for Python 3

A few remotefilelog tests still fail on Python 3, but it's a much better story
now.

Differential Revision: https://phab.mercurial-scm.org/D5609

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