* upstream-master:
  Remove long-deprecated scheduler config variable alternatives (spotify#2491)
  Bump tornado milestone version (spotify#2490)
  Update moto to 1.x milestone version (spotify#2471)
  Use passed password when create a redis connection (spotify#2489)
  S3 client refactor (spotify#2482)
  Rename to rpc_log_retries, and make it apply to all the logging involved
  Factor log_exceptions into a configuration parameter
  Fix attribute forwarding for tasks with dynamic dependencies (spotify#2478)
  Add a visiblity level for luigi.Parameters (spotify#2278)
  Add support for multiple requires and inherits arguments (spotify#2475)
  Add metadata columns to the RDBMS contrib (spotify#2440)
  Fix race condition in luigi.lock.acquire_for (spotify#2357) (spotify#2477)
  tests: Use RunOnceTask where possible (spotify#2476)
  Optional TOML configs support (spotify#2457)
  Added default port behaviour for Redshift (spotify#2474)
  Add codeowners file with default and specific example (spotify#2465)
  Add Data Revenue to the `blogged` list (spotify#2472)
  Fix Scheduler.add_task to overwrite accepts_messages attribute. (spotify#2469)
  Use task_id comparison in Task.__eq__. (spotify#2462)

* upstream-master:
  Fix S3Client.copy return value consistency (spotify#2488)
  s3client check for deprecated host keyword and raise error with the details (spotify#2493)
  Fix exception when toml lib is not installed (spotify#2506)
  Add Okko to companies that use luigi (spotify#2512)
  Added optional choice for hdfs clients  (spotify#2487)
  Version 2.7.8
  revert tornado upgrade
  Version 2.7.7
  added a new event 'progress' (spotify#2498)
  Add Uppsala University / pharmb.io as user (spotify#2496)