This prevents this overlay's python override from replacing other python
overrides put in place by other overlays that are also in use

pyopenssl 20.0.1 requires cryptography 3.2...

Also add a test for openssl runtime version matching packaging version

actually, test fails, so it demonstrates we don't

not yet built locally because slow networks and computers and such
let's see what CI does with it

The previous version did pin nixpkgs to the version in nixpkgs.json.  However,
it did so without a name which means the derivation was only cacheable for a
few minutes.

By supplying name the resulting derivation can now be stored in /nix/store and
re-used as long as the hash does not change.

Run vulnerability scan on CI

See merge request opensource/PrivateStorageio!64

still pretty hard to consume