tests/narrow-library.sh

py3: convert bytes to str using encoding.strfromlocal

using encoding.strfromlocal because sender is provided from user config or
argument.

Differential Revision: https://phab.mercurial-scm.org/D2460

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