Creates a symlink to the .so file in postint for mod_wsgi

[kushaldas]

Status

Ready for review

Description of Changes

Fixes in part of #4768

On Focal, mod_wsgi expects a shared library for the python module at:

$VENV/lib/python3.8/site-packages/mod_wsgi/server/mod_wsgi-py38.so

But, the real shared library path is

$VENV/lib/python3.8/site-packages/mod_wsgi/server/mod_wsgi-py38.cpython-38-x86_64-linux-gnu.so"

So we are creating a symlink with the proper path if we are using Python 3.8 (that is on Focal)

Testing

• make build-deps on this branch
• make staging to create a fresh staging environment from the debian packages. There should not be any error in the postinstall section
• Login to app molecule -s libvirt-staging-xenial -h app-staging (on mac point to virtualbox) and see that the following file does not exist.

/opt/venvs/securedrop-app-code/lib/python3.8/site-packages/mod_wsgi/server/mod_wsgi-py38.so

• sudo touch /usr/bin/python3.8 to emulate a python3.8 env in focal
• reinstall the securedrop-app-code package or reconfigure it, it should create a symlink as mentioned above.

Deployment

Any special considerations for deployment? Consider both:

1. Upgrading existing production instances.
2. New installs.

Checklist

If you made changes to the server application code:

• Linting (make lint) and tests (make test) pass in the development container

If you made changes to securedrop-admin:

• Linting and tests (make -C admin test) pass in the admin development container

If you made changes to the system configuration:

• Configuration tests pass

If you made non-trivial code changes:

• I have written a test plan and validated it for this PR

If you made changes to documentation:

• Doc linting (make docs-lint) passed locally

If you added or updated a code dependency:

Choose one of the following:

• I have performed a diff review and pasted the contents to the packaging wiki
• I would like someone else to do the diff review

[kushaldas]

This is continuation of #5443

[rmol]

I finally figured out why the mod_wsgi configuration was broken. The Ubuntu box used in the libvirt staging environment somehow lacks the python3-distutils package. When running mod_wsgi-express module-config, that causes this import to fail, bypassing the determination of the shared library naming scheme, specifically this.

The generic Ubuntu installation used in the Qubes staging environment has python3-distutils by default, so I never saw this failure.

I think the best fix is adding python3-distutils as a dependency of securedrop-app-code, which I've done in #5484. So now if you build the Focal debs on that branch, then check out the branch of #5486, you get a working mod_wsgi configuration.

[conorsch]

Thanks for the clarification, @rmol. #5484 is now merged, and #5486 has been rebased to include it, so we should be unblocked to proceed with review over there.

@kushaldas Should we then close this PR? Or would you prefer to test #5486 first?

[kushaldas]

I thought I closed this one, it seems I only closed the issue and forgot the pr.