Change all C code to return ndn_Error enum instead of char * error string.
diff --git a/test/test-encode-decode-interest.cpp b/test/test-encode-decode-interest.cpp
index 467584c..ead57cc 100644
--- a/test/test-encode-decode-interest.cpp
+++ b/test/test-encode-decode-interest.cpp
@@ -51,7 +51,7 @@
     cout << "Interest encoding length " << encodingLength << " vs. sizeof(Interest1) " << sizeof(Interest1) << endl;
 #endif
   } catch (exception &e) {
-    cout << "exception " << e.what() << endl;
+    cout << "exception: " << e.what() << endl;
   }
   return 0;
 }