go/build: change the wording of NoGoError and comment it better Out of context, it can be very confusing because there can be lots of Go files in the directory, but the error message says there aren't.
go/build: change the wording of NoGoError and comment it better
Out of context, it can be very confusing because there can be lots of Go
files in the directory, but the error message says there aren't.

R=golang-dev, dsymonds, rsc
CC=golang-dev
https://codereview.appspot.com/12823043

tv42/old-go,pombredanne/go-deleteme,tv42/old-go,apparentlymart/golang,apparentlymart/golang,tv42/old-go,apparentlymart/golang,apparentlymart/golang,tv42/old-go,pombredanne/go-deleteme,tv42/old-go,apparentlymart/golang,tv42/old-go,pombredanne/go-deleteme,apparentlymart/golang,pombredanne/go-deleteme,pombredanne/go-deleteme,pombredanne/go-deleteme,apparentlymart/golang,pombredanne/go-deleteme,tv42/old-go