1696526 - (ci-py3) [meta] Run all tasks in CI with Python 3

Status: RESOLVED FIXED

(Firefox Build System :: Task Configuration, task)

Description

[Andrew Halberstadt [:ahal]]

Work to support Python 3 in our test harnesses and build system has largely been completed (with a few stragglers). But most of these still run against Python 2 in CI. We should attempt to switch everything we can over to running with Python 3. Once that happens, we'll be able to drop Python 2 support.

In general this will look like:

1. Add the python-3: true config to the task definition
2. Test on try to make sure everything passes (fix things that break)
3. Once all tasks for a given code module are switched over, add an exclude rule to the py2 linter so we can start using Python 3-only syntax there.