Add Ubuntu2604 builds to CI

[Victor-Schwan]

BEGINRELEASENOTES

• Add Ubuntu2604 builds to CI

ENDRELEASENOTES

[tmadlener]

Ubuntu 26 container is now available. We are running into the following now. this looks familiar, but I don't know from where.

    Traceback (most recent call last):
      File "/cvmfs/sft-nightlies.cern.ch/lcg/views/devkey-head/Wed/x86_64-ubuntu2604-gcc15-opt/bin/ddsim", line 21, in <module>
        RUNNER.parseOptions()
        ~~~~~~~~~~~~~~~~~~~^^
      File "/cvmfs/sft-nightlies.cern.ch/lcg/views/devkey-head/Wed/x86_64-ubuntu2604-gcc15-opt/lib/python3.13/site-packages/DDSim/DD4hepSimulation.py", line 146, in parseOptions
        self.readSteeringFile()
        ~~~~~~~~~~~~~~~~~~~~~^^
      File "/cvmfs/sft-nightlies.cern.ch/lcg/views/devkey-head/Wed/x86_64-ubuntu2604-gcc15-opt/lib/python3.13/site-packages/DDSim/DD4hepSimulation.py", line 124, in readSteeringFile
        exec(compile(io.open(self.steeringFile).read(), self.steeringFile, 'exec'), globs, locs)
        ~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
      File "ddsim_steer.py", line 252, in <module>
        SIM.physics.pdgfile = os.path.join( os.environ.get("DD4HEP"),  "DDG4/examples/particle.tbl")
                              ~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
      File "<frozen posixpath>", line 77, in join
    TypeError: expected str, bytes or os.PathLike object, not NoneType

[andresailer]

DD4HEP variable not defined?

[tmadlener]

Yeah, that sounds like it could be the problem. I haven't verified this though.