websocket: better error message in a test
websocket: better error message in a test

R=golang-dev, dsymonds
CC=golang-dev
http://codereview.appspot.com/5185045

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