2.8.0

This is a minor version bump, due to:

• Dropping Python 3.4 and 3.5 from CI, which means no automated tests to ensure compatibility for those versions
• [Security Patch] CORS being disabled by default. A new section of configuration [cors] is introduced to enable custom settings. For details, refer to user group topic: https://groups.google.com/forum/#!topic/luigi-user/ZgfRTpBsVUY

Added

luigi:

• Add Python 3.7 compatibility (#2466)
  This also drops 3.4 and 3.5 from CI.
• Interpolate environment variables in .cfg config files (#2527)

luigi.contrib:

• Add CopyToTable task for MySQL (#2553)
• Add HdfsFlagTarget (#2559)

luigi.contrib:

Fixed

luigi:

• Fix ReadTheDocs build (#2546)
• Make capture_output non-positional in ExternalProgramTask (#2547)

luigi.contrib:

• Fix S3Client's _path_to_bucket_and_key to support keys with question marks (#2534)
• Fix S3Client.remove - add max batch size (#2529)
• Small fix to logging in contrib/ecs.py (#2556)
• FIX HdfsAtomicWriteDirPipe.close() when using snakebite and the file do not exist. (#2549)

Changed:

luigi:

• [ImgBot] optimizes images (#2555)

luigi.contrib:

• Remove s3 bucket validation prior to file upload (#2528)
• Refactor s3 copy into sub-methods (#2508)