NNLO ttbar xsec, and some v18 bookkeeping.
Submit script: use Samples.from_argv, clean up ex(n).
pprint takes list of batches to print (for e.g. cleanup).
Import regular pprint as _pprint for use when interactive.
pprint batches argument can take seq of seqs for specifying sample order.
Clean out old, deleted files.
Hint on cleaning.
Move SampleFiles dict to separate file just for it.