Merge branch 'release/4.8.6' into develop
fix flower broker_api generation.
Make git_update() sparks aware.
flake8.
Make migrate() sparks aware.
oops. forgot argument.
fix args passing. always kwargs it.
more worker queues names available.
allow to get BROKER_API from the environment to circumvent OS versions woes easily.
bump version.
Merge branch 'release/4.9'