Installer: Clean up RepoIO interface

Change-Id: If80d7be1460c725b7df9d1d27c9354cb9141acfe
diff --git a/core/installer/cmd/env_manager.go b/core/installer/cmd/env_manager.go
index 196110f..0142bee 100644
--- a/core/installer/cmd/env_manager.go
+++ b/core/installer/cmd/env_manager.go
@@ -64,7 +64,10 @@
 		return err
 	}
 	log.Printf("Cloned repo: %s\n", envManagerFlags.repoName)
-	repoIO := installer.NewRepoIO(repo, sshKey.Signer())
+	repoIO, err := installer.NewRepoIO(repo, sshKey.Signer())
+	if err != nil {
+		return err
+	}
 	nsCreator, err := newNSCreator()
 	if err != nil {
 		return err