message: buildenv: Protect against missing drake metadata directory.
diff: @@ -267,7 +267,11 @@ class State:
  to = '%s/.drake/%s' % (tmp, to)
  mkpath(os.path.dirname(to))
  rm(to)
  + if os.path.exists(fr):
  mv(fr, to)
  + else:
  + print('%s: missing drake directory: %s' % (sys.argv[0], fr),
  + file = sys.stderr)
  except:
  rm(tmp)
  raise
  