Resolve error handling/parser related TODOs

See #5324

tpl/data/data.go

@@ -120,7 +120,6 @@ func (ns *Namespace) GetJSON(urlParts ...string) (v interface{}, err error) {
 
 	if err != nil {
 		return nil, _errors.Wrapf(err, "failed to get getJSON resource %q", url)
-		return nil, nil
 	}
 	return
 }

tpl/template.go

@@ -179,7 +179,7 @@ func (t *TemplateAdapter) addFileContext(name string, inerr error) error {
 		}
 		return false
 	}
-	// TODO(bep) 2errors text vs HTML
+
 	fe, ok := herrors.WithFileContext(ferr, realFilename, f, lineMatcher)
 	if ok || !hasMaster {
 		return fe