wireprotoserver: ensure that output stream gets flushed on exception
Previously flush was happening due to Python finalizer being run on
`BufferedWriter`. With upgrade to Python 3.11 this started randomly
failing.
My guess is that the finalizer on the raw `FileIO` object may
be running before the finalizer of `BufferedWriter` has a chance to run.
At any rate, since we're not relying on finalizers in the happy case
we should also not rely on them in case of exception.
$ hg init test
$ cat >hgweb.cgi <<HGWEB
> #!$PYTHON
> from mercurial import demandimport; demandimport.enable()
> from mercurial.hgweb import hgweb
> from mercurial.hgweb import wsgicgi
> application = hgweb(b"test", b"Empty test repository")
> wsgicgi.launch(application)
> HGWEB
$ chmod 755 hgweb.cgi
Check that non-ASCII bytes roundtrip correctly.
$ . "$TESTDIR/cgienv"
$ PATH_INFO="/rev/$(python -c 'import sys; sys.stdout.buffer.write(b"\xe2\x80\x94")')"; export PATH_INFO
$ QUERY_STRING="style=raw"; export QUERY_STRING
$ "$PYTHON" ./hgweb.cgi | grep error
error: unknown revision '\xe2\x80\x94' (esc)