"cannot find package" errors could be more informative #290
Description
Consider this error from gopherjs build:
cannot find package "github.com/flimzy/flashback/pages" in any of:
/usr/local/go/src/github.com/flimzy/flashback/pages (from $GOROOT)
/home/jonhall/go/src/github.com/flimzy/flashback/pages (from $GOPATH)
It's almost identical to the same error from go build:
cmd/server/server.go:4:2: cannot find package "oink" in any of:
/usr/local/go/src/oink (from $GOROOT)
/home/jonhall/go/src/oink (from $GOPATH)
Except that the go version tells me where the missing dependency is referenced ("cmd/server.go:4:2").
It would be very handy if GopherJS did the same thing :)