error rewording suggested by robert. update comment.
error rewording suggested by robert.
update comment.

R=ken
http://go/go-review/1025031

pombredanne/go-deleteme,h8liu/golang,bdwalton/debian-golang,tv42/old-go,pombredanne/go-deleteme,tianon/debian-golang,nightlyone/golang,pombredanne/go-deleteme,bdwalton/debian-golang,dsriram/golang,tianon/debian-golang,h8liu/golang,ssrl/go,nightlyone/golang,tv42/old-go,h8liu/golang,apparentlymart/golang,tv42/old-go,dsriram/golang,gnanderson/go,h8liu/golang,tv42/old-go,bdwalton/debian-golang,apparentlymart/golang,gnanderson/go,pombredanne/go-deleteme,nightlyone/golang,bdwalton/debian-golang,dsriram/golang,dsriram/golang,tv42/old-go,h8liu/golang,gnanderson/go,dsriram/golang,ssrl/go,h8liu/golang,gnanderson/go,dsriram/golang,tianon/debian-golang,tv42/old-go,bdwalton/debian-golang,tianon/debian-golang,bdwalton/debian-golang,apparentlymart/golang,nightlyone/golang,tianon/debian-golang,ssrl/go,h8liu/golang,pombredanne/go-deleteme,bdwalton/debian-golang,nightlyone/golang,ssrl/go,nightlyone/golang,ssrl/go,apparentlymart/golang,apparentlymart/golang,tianon/debian-golang,bdwalton/debian-golang,tianon/debian-golang,nightlyone/golang,pombredanne/go-deleteme,dsriram/golang,apparentlymart/golang,ssrl/go,gnanderson/go,gnanderson/go,gnanderson/go,pombredanne/go-deleteme,tv42/old-go,ssrl/go,apparentlymart/golang,tianon/debian-golang