Commit e42648dccd "qapi/expr.py: Remove single-letter variable"
accidentally removed the check for "only lower case letters and
hyphens". Restore it.
Fixes: e42648dccd
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <20220510061645.3209195-2-armbru@redhat.com>