Changed logging to avoid overflow (#302)

Author: lupengamzn

aws_xray_sdk/core/utils/conversion.py

@@ -31,5 +31,5 @@ def metadata_to_dict(obj):
         else:
             return obj
     except Exception:
-        log.exception("Failed to convert {} to dict".format(str(obj)))
+        log.exception("Failed to convert metadata to dict")
         return {}