Sqs-workers

Added

- Allow to override `sqs_client`, `sqs_resource` by passing them the `SQSEnv` constructor.

Added

- New codec (message encoding) that uses the default version of the Pickle protocol instead of one compatible with Python 2.
- Possibility to change default codec in SQSEnv.

Changed

- When a processor for a job can't be found, we now log this as an error (rather than a warning) and provide a more helpful error message.
- Default codec is renamed from "pickle" to "pickle_compat".

Changed

- Supporting batch read sizes over 10 messages by using multiple calls to SQS

Added

- Ability to configure a queue to send batches of messages to a
handling function rather than processing them individually
- Contributing file to guide submitting PRs

Changed

- Using `%s` string interpolation for logging, easier for tools
like Sentry / DataDog to group similar messages when parsing
- Using type annotations over type comments now Python 2.7 support has been dropped
- Moved to Poetry for dependency management & packaging

Fixed

- Fixed a behavior change for the utils.validate_arguments function

Changed

- Dropped support for Python 2
- Declared Python 3.8 as the minimum version supported
- Dropped 2 dependencies (werkzeug and future) that are not needed anymore
- Updated README a bit

Fixed

- Fixed a bug with recent versions of Werkzeug (20)