Use python's logging module instead of print

When running the commit script on hundreds of files buffering of the stderr/out seems to mangle the output.

./scripts/commit_new_dsid.sh -n -d=421332-421475
INFO: will use following remote for pushing: origin
Checking jO consistency and DSID ranges ...
ERROR in jO consistency checks
ERROR: file 421xxx/421332/mc.MGPy8EG_A14N23LO_VBFWBCpCp_150_145_MET75_MS.py

We should switch to using python's logging module or handle this in a smarter way so that flushing is handled in a better way.

Reported by @gstark