cmd/coordinator: fix build; don't less err context

Change-Id: I1f3a9631e0fe0144717b1ee9fc96f23b688212a7
Reviewed-on: https://go-review.googlesource.com/16959
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
diff --git a/cmd/coordinator/kube.go b/cmd/coordinator/kube.go
index 2a56dda..2f082d8 100644
--- a/cmd/coordinator/kube.go
+++ b/cmd/coordinator/kube.go
@@ -55,9 +55,10 @@
 		return errors.New("coordinator not running with access to the Cloud Platform scope.")
 	}
 	httpClient := oauth2.NewClient(oauth2.NoContext, tokenSource)
+	var err error
 	containerService, err = container.New(httpClient)
 	if err != nil {
-		return fmt.Errorf("could not create client for Google Container Engine")
+		return fmt.Errorf("could not create client for Google Container Engine: %v", err)
 	}
 
 	cluster, err := containerService.Projects.Zones.Clusters.Get(projectID, projectZone, clusterName).Do()