message: Create workdir if needed.
diff: @@ -3145,6 +3145,8 @@ def run(root, *cfg, **kwcfg):
  workdir = True
  if workdir is True:
  raise Exception('missing argument for option {}'.format(arg))
  + if workdir is not None and not _OS.path.exists(workdir):
  + _OS.makedirs(workdir)
  with Drake(root = root, workdir = workdir) as d:
  d.run(*cfg, **kwcfg)
  