Add a MustNamespace that panics if the namespace wasn't valid

filter/count/gi.go

Index: filter/count/gi.go
diff --git a/filter/count/gi.go b/filter/count/gi.go
index e2fff3bc5e34a9602e4fc1c06232b6f8f9d39a1c..5524af003721ebe64f3bb40e3ce4a43bc8c67a5d 100644
--- a/filter/count/gi.go
+++ b/filter/count/gi.go
@@ -30,6 +30,7 @@ type InfoCounter struct {
 	ServiceAccount         Entry
 	VersionID              Entry
 	Namespace              Entry
+	MustNamespace          Entry
 	AccessToken            Entry
 	PublicCertificates     Entry
 	SignBytes              Entry
@@ -123,6 +124,11 @@ func (g *infoCounter) Namespace(namespace string) (context.Context, error) {
 	return ret, g.c.Namespace.up(err)
 }
 
+func (g *infoCounter) MustNamespace(namespace string) context.Context {
+	g.c.MustNamespace.up()
+	return g.gi.MustNamespace(namespace)
+}
+
 func (g *infoCounter) AccessToken(scopes ...string) (string, time.Time, error) {
 	token, expiry, err := g.gi.AccessToken(scopes...)
 	return token, expiry, g.c.AccessToken.up(err)