Hi!

While rebuilding the python related packages against the Python 3.15rc2
version we found that gensim fails to build from source due to
build-depending on python3-pyemd, which is not installable.

This is easy to fix, as gensim doesn't really need pyemd, it's already
migrated to pot.

I also took the opportunity to fix the tests, by installing
ca-certificates.

I've applied the upstream fix in the sandbox [1] to verify that it
builds successfully, please consider applying the patch to make the
package buildable once again.

Happy hacking,

[1]: https://debusine.debian.net/debian/r-python-python3.15/