0.11.0: Fix race condition, improve resource usage

Migrations

• https://github.com/peopledoc/procrastinate/blob/master/procrastinate/sql/migrations/delta_0.10.0_001_close_fetch_job_race_condition.sql
• https://github.com/peopledoc/procrastinate/blob/master/procrastinate/sql/migrations/delta_0.10.0_002_add_defer_job_function.sql

Breaking changes

• If you created an AiopgConnector with maxsize=0 or 1, it used to change it to 2. Now it won't. 0 should really be avoided. 1 will disable the listen/notify feature. See doc.

Features

• Synchronous programs can now define a Psycopg2Connector() and have real synchronous I/Os, likely to work better with multithreaded programs. See doc. (#237)
• Default log message contains task result. This means you can return <something> in your task to make this <something> appear in your logs (#252)
• Make listen/notify optional, through listen_notify=False in your worker configuration (#258)

Bug Fixes

• Close race condition in procrastinate_fetch_job (#231)
• Retry on "server closed connection unexpectedly" errors (#259)
• Synchronous closing for AiopgConnector (#263)
• Add task.defer as an explicit sync method (#257)

Miscellaneous

• Documentation "Quickstart" section was full of imprecisions (#254)
• Display test results & simplify Tox setup (#253)
• Add function procrastinate_defer_job (#232)
• CONTRIBUTING.rst: more precise wording on release automated steps (#248)
• Update release-drafter.yml (#245)

Kudos:

@elemoine and @ewjoachim