Don't permanently add zip DAGs to sys.path

[jedcunningham]

Only leave the zip on sys.path while parsing that zip file, as we
shouldn't assume parsing only happens in separate processes. For
example, resetdb is used to run migrations, some of which parse
the DAGs.

[github-actions]

The PR most likely needs to run full matrix of tests because it modifies parts of the core of Airflow. However, committers might decide to merge it quickly and take the risk. If they don't merge it quickly - please rebase it to the latest main at your convenience, or amend the last commit of the PR, and push it with --force-with-lease.

[potiuk]

Do I get correctly - that was causing the side-effect of failing KPO tests in some cases?

[jedcunningham]

PodGenerator, yeah. Some tests in test_pod_generator.py use sys.path[0] and expect it to have cwd:

airflow/tests/kubernetes/test_pod_generator.py

Line 164 in c686241

path = sys.path[0] + '/tests/kubernetes/pod_generator_base_with_secrets.yaml'

However a couple migrations parse the DAGs and this was leaving the zip in spot 0 (in fact, it would be [zip, zip, cwd, ...]). You could force the issue every time using --with-db-init. Granted, the tests probably shouldn't rely on sys.path[0] being unmodified either, but this PR at least fixed the real issue.