diff --git a/cmd/runtimetest/main.go b/cmd/runtimetest/main.go
index <HASH>..<HASH> 100644
--- a/cmd/runtimetest/main.go
+++ b/cmd/runtimetest/main.go
@@ -68,7 +68,7 @@ func loadSpecConfig(path string) (spec *rspec.Spec, err error) {
 	cf, err := os.Open(configPath)
 	if err != nil {
 		if os.IsNotExist(err) {
-			return nil, fmt.Errorf("%s not found", specConfig)
+			return nil, specerror.NewError(specerror.ConfigInRootBundleDir, err, rspec.Version)
 		}
 
 		return nil, err
runtimetest: Raise ConfigInRootBundleDir for missing config.json

This is a bit tricky, because before we load the config, we don't know
the target spec version.  If a future spec version relaxes the current
requirement, we'll have difficulty reporting an "I couldn't find the
config" error as a spec violation.  If/when that happens, I'm fine
dropping this block altogether, and having this error fall through as
a non-spec "you called us wrong" error.