Debugging urdf parsing problems in gazebo_ros

I am trying to create a gazebo model for a robot. Using a collection of xacro files I generate a urdf and then spawn a robot using gazebo_ros, all in a launch file. Unfortunately this doesn't work and the only hint I get is:> Error [parser_urdf.cc:2768] Unable to> call parseURDF on robot model Is there a way to debug such errors and know exactly which line on my urdf is causing the problem without digging into parser_urdf.cc ? I am using Gazebo 4.1.2 with ROS Indigo on Ubuntu 14.04