qapi/introspect.py: assert schema is not None

The introspect visitor is stateful, but expects that it will have a
schema to refer to. Add assertions that state this.

Signed-off-by: John Snow <jsnow@redhat.com>
Message-Id: <20210216021809.134886-3-jsnow@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
1 file changed