This error message should reference t2, not t1.

Change-Id: I2e42b8335ca9367a1fb7f76c38a1bcf8f32a2bf3
Reviewed-on: https://go-review.googlesource.com/82816Reviewed-by: Gabriel Aszalos <gabriel.aszalos@gmail.com>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Gabriel Aszalos <gabriel.aszalos@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>