Added AssertionError raising for check of invalid leaf nodes.

Former-commit-id: 7582a967e84eec1713d91c78c004de8ea2b913da

kadmos/graph/graph_kadmos.py

@@ -4671,6 +4671,9 @@ def _check_leafs(io_list, leafs):
                         logger.debug('Invalid leaf element path {}'.format(leaf[1]))
                         logger.debug('Reason for invalidity: longer path {} found in file {}'.format(path, file_name))
                         leafs.remove(leaf)
+                        raise AssertionError('Invalid leaf element found in XML file {}\n'.format(leaf[2]) +
+                                             'Invalid leaf element path {}\n'.format(leaf[1]) +
+                                             'Reason for invalidity: longer path {} found in file {}'.format(path, file_name))
     return