cmd/getgo: fix vet failure caused by missing argument to Errorf call.
cmd/getgo: fix vet failure caused by missing argument to Errorf call.

Change-Id: I2812e2c655a0e463203f5c2ede08182c40556953
Reviewed-on: https://go-review.googlesource.com/75975
Reviewed-by: Gabriel Aszalos <08a2f807ca69c12efc020bd863a19890e920f1c4@gmail.com>
Reviewed-by: Brad Fitzpatrick <ae9783c0b0efc69cd85ab025ddd17aa44cdc4aa5@golang.org>
Run-TryBot: Gabriel Aszalos <08a2f807ca69c12efc020bd863a19890e920f1c4@gmail.com>

golang/tools,golang/tools,golang/tools,golang/tools,golang/tools