tests: clean up bad extension
The presence of the "babar" extension breaks subsequent tests.
So delete the file and create an empty one to return the config
to sanity.
#require test-repo
$ . "$TESTDIR/helpers-testrepo.sh"
$ cd "$TESTDIR"/..
New errors are not allowed. Warnings are strongly discouraged.
$ hg files "set:(**.py or **.txt) - tests/**" | sed 's|\\|/|g' |
> python contrib/check-config.py