Merge remote-tracking branch 'remotes/cleber-gitlab/tags/python-next-pull-request' into staging

Acceptance and Python Test Improvements

Small collection of Acceptance and Python tests/improvements.

# gpg: Signature made Wed 17 Mar 2021 03:22:47 GMT
# gpg:                using RSA key 7ABB96EB8B46B94D5E0FE9BB657E8D33A5F209F3
# gpg: Good signature from "Cleber Rosa <crosa@redhat.com>" [marginal]
# gpg: WARNING: This key is not certified with sufficiently trusted signatures!
# gpg:          It is not certain that the signature belongs to the owner.
# Primary key fingerprint: 7ABB 96EB 8B46 B94D 5E0F  E9BB 657E 8D33 A5F2 09F3

* remotes/cleber-gitlab/tags/python-next-pull-request:
  tests/acceptance: linux-related tests fix
  tests: Add functional test for out-of-process device emulation
  avocado_qemu: add exec_command function
  tests/migration: fix unix socket batch migration
  tests/acceptance: Print expected message on wait_for_console_pattern

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