code: func ExpectAlreadyExists(c *check.C, err error) {
  	c.Assert(trace.IsAlreadyExists(err), check.Equals, true, check.Commentf("expected AlreadyExists, got %T %v at %v", trace.Unwrap(err), err, string(debug.Stack())))
  }
docs: // ExpectAlreadyExists expects already exists error