Merge remote-tracking branch 'remotes/armbru/tags/pull-qapi-2020-03-05' into staging

QAPI patches for 2020-03-05

# gpg: Signature made Thu 05 Mar 2020 12:42:15 GMT
# gpg:                using RSA key 354BC8B3D7EB2A6B68674E5F3870B400EB918653
# gpg:                issuer "armbru@redhat.com"
# gpg: Good signature from "Markus Armbruster <armbru@redhat.com>" [full]
# gpg:                 aka "Markus Armbruster <armbru@pond.sub.org>" [full]
# Primary key fingerprint: 354B C8B3 D7EB 2A6B 6867  4E5F 3870 B400 EB91 8653

* remotes/armbru/tags/pull-qapi-2020-03-05:
  qapi: Brush off some (py)lint
  qapi: Use super() now we have Python 3
  qapi: Drop conditionals for Python 2
  qapi: Inheriting from object is pointless with Python 3, drop

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>