Do not import ROOT when using podio-dump --help

[jmcarcell]

BEGINRELEASENOTES

• Do not import ROOT when using podio-dump --help, otherwise it can take a while depending on the system only to print the help.

ENDRELEASENOTES

Small quality of life improvement to make it a bit less painful when running from cvmfs.

[tmadlener]

Ah right, this changed with #484 I think. Previously the from podio import __version__ was exactly there to have a quick podio-dump --help and podio-dump --version.

I would propose to keep the current __version__ file because that is what "normal" python packages do and simply create a second podio_version.py with the same contents already at the cmake stage. That will also automatically make pre-commit and the tests happy, because they all assume that they are run before installing things.

[tmadlener]

Thanks a lot for this.