add error handling/reporting for client module

Change-Id: I38875e561aa85093030ad6f937891723bd401de2
diff --git a/src/protocol-detail/error.cpp b/src/protocol-detail/error.cpp
index 739c3b7..b74180b 100644
--- a/src/protocol-detail/error.cpp
+++ b/src/protocol-detail/error.cpp
@@ -42,5 +42,12 @@
   return std::make_tuple(error, description);
 }
 
+bool
+ErrorTLV::isErrorContent(const Block& block)
+{
+  block.parse();
+  return block.find(tlv_error_code) != block.elements_end();
+}
+
 }  // namespace ndncert
 }  // namespace ndn