AU: FilesystemCopierAction: copy bit-exactly

Review URL: http://codereview.chromium.org/1700018
diff --git a/utils.cc b/utils.cc
index 7f05ffb..724a4ba 100644
--- a/utils.cc
+++ b/utils.cc
@@ -333,6 +333,12 @@
   return true;
 }
 
+const char* GetGErrorMessage(const GError* error) {
+  if (!error)
+    return "Unknown error.";
+  return error->message;
+}
+
 const char* const kStatefulPartition = "/mnt/stateful_partition";
 
 }  // namespace utils