Merge remote-tracking branch 'remotes/kevin/tags/for-upstream' into staging

Merge remote-tracking branch 'remotes/kevin/tags/for-upstream' into staging

Block layer patches:

- iotests: Fix pylint/mypy warnings with Python 3.9
- qmp: fix aio_poll() assertion failure on Windows
- Some minor fixes

# gpg: Signature made Tue 03 Nov 2020 15:25:01 GMT
# gpg:                using RSA key DC3DEB159A9AF95D3D7456FE7F09B272C88F2FD6
# gpg:                issuer "kwolf@redhat.com"
# gpg: Good signature from "Kevin Wolf <kwolf@redhat.com>" [full]
# Primary key fingerprint: DC3D EB15 9A9A F95D 3D74  56FE 7F09 B272 C88F 2FD6

* remotes/kevin/tags/for-upstream:
  block/vvfat: Fix bad printf format specifiers
  iotests: Use Python 3 style super()
  iotests: Disable unsubscriptable-object in pylint
  iotests.py: Fix type check errors in wait_migration()
  qemu-img convert: Free @sn_opts in all error cases
  qmp: fix aio_poll() assertion failure on Windows

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