message: replace comprehension with generator expression. (why isnt this a lint?)
diff: @@ -74,8 +74,8 @@ def main(argv):
  while dirs:
  d = dirs.pop()
  for path, newdirs, files in os.walk(d):
  - tf_records.extend([os.path.join(path, f) for f in files if f.endswith('.zz')])
  - dirs.extend([os.path.join(path, d) for d in newdirs])
  + tf_records.extend(os.path.join(path, f) for f in files if f.endswith('.zz'))
  + dirs.extend(os.path.join(path, d) for d in newdirs)
  else:
  tf_records = validation_paths
  