fix lint CI race condition

[djrtwo]

Lint CI requires install_test and was sometimes failing due to a race condition.

fixed!

[hwwhww]

lint job doesn't require install_test (make install_test). Instead, it installs flake8 with make intall_lint.

But it seems we should make it requires checkout_specs.

      - lint:
          requires:
            - checkout_specs

[djrtwo]

neither install_test nor checkout_specs actually build the pyspec

Here is an instance of the error. Because test builds the pyspec, I think we should just have it as a dependency of test. Thoughts?

[hwwhww]

@djrtwo Ahh, you're right about that both test and lint jobs build pyspec. I also realized that only install_test does save_cached_venv so flake8 installation isn't part of the stored cache! I updated it to install_env job.

If we make lint requires test, the workflow becomes:

Sorry for the spam commits of the experiment on this branch. I was thinking about if we can utilize parallel jobs to:

But it seems to require reworking Makefile... so I'm inclined to keep serial workflow for now.