message: Switch ClusterSpec's __str__ to __repr__.
  str is generally human readable, while repr is an eval-ready reproduction
  string. The existing implementation of __str__ is eval-ready.
  The default __str__ calls __repr__, so the test for this function is still
  valid.
diff: @@ -325,7 +325,7 @@ class ClusterSpec(object):
  def __ne__(self, other):
  return self._cluster_spec != other
  - def __str__(self):
  + def __repr__(self):
  key_values = self.as_dict()
  string_items = [
  repr(k) + ": " + repr(key_values[k]) for k in sorted(key_values)
  