Appengine compilation fail

I recently upgraded one of my services to use logging. I set it up with the exact same lines you have here:

```go
// Configure logging for appengine
w := log.NewSyncWriter(os.Stderr)
logger := log.NewLogfmtLogger(w)

// Create goa application
service := goa.New("myService")
service.WithLogger(goakit.New(logger))
```

This causes my build on appengine to error with this:

```
ERROR: (gcloud.app.deploy) Error Response: [9] Deployment contains files that cannot be compiled: Compile failed:
2017/06/21 18:45:06 go-app-builder: build timing: 18×compile (5.536s total), 0×link (0s total)
2017/06/21 18:45:06 go-app-builder: failed running compile: exit status 15
```

When I remove these lines, and just create the service instead, I am able to successfully build on appengine. I wish the appengine build tool gave a more descriptive error. I read through the logs, and they were not helpful either. I'm definitely willing to contribute towards fixing the issue if we can find it.