demande-import-test: use `wsgiref` instead of `telnetlib` for testing
The `telnetlib` module has been dropped in 3.13. The `wsgiref` module fit the
same purpose of being obscure and not imported yet.
#require emacs
$ emacs -q -no-site-file -batch -l $TESTDIR/../contrib/hg-test-mode.el \
> -f ert-run-tests-batch-and-exit
Running 1 tests (*) (glob)
passed 1/1 hg-test-mode--compilation-mode-support* (glob)
Ran 1 tests, 1 results as expected* (glob)