test: change bug040 to use errorcheck
test: change bug040 to use errorcheck

Because bug040.go was ignoring all error messages, the fact
that it got an error about fuction main was being ignored.

R=golang-dev, r
CC=golang-dev
http://codereview.appspot.com/5675085

h8liu/golang,h8liu/golang,h8liu/golang,h8liu/golang,h8liu/golang,h8liu/golang,h8liu/golang