tests/narrow-library.sh

typing: add an assertion instead of blacklisting mercurial/extensions.py

Differential Revision: https://phab.mercurial-scm.org/D10175

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