GET to restconf/modules returns 500 with exception

A GET call to restconf/modules is suppose to tell you what the supported modules are in the system, however in ODL it is returing a 500, indicating an internal problem.

The issue is that the ietf-restconf.yang is not shipped with the project, but is a hardcoded lookup. Thus when the lookup happens it fails to find the file and thus fails.

Solution ship the ietf-restconf.yang file from yangtools.