Compatibility with Orocos KDL after Joint.None was removed

See ros#45

Author: fjulian

kdl_parser_py/kdl_parser_py/urdf.py

@@ -50,7 +50,10 @@ def _toKdlInertia(i):
 
 def _toKdlJoint(jnt):
 
-    fixed = lambda j,F: kdl.Joint(j.name, getattr(kdl.Joint, "None"))
+    fixed = lambda j,F: kdl.Joint(
+        j.name,
+        getattr(kdl.Joint, "Fixed") if hasattr(kdl.Joint, 'Fixed') else getattr(kdl.Joint, 'None')
+    )
     rotational = lambda j,F: kdl.Joint(j.name, F.p, F.M * kdl.Vector(*j.axis), kdl.Joint.RotAxis)
     translational = lambda j,F: kdl.Joint(j.name, F.p, F.M * kdl.Vector(*j.axis), kdl.Joint.TransAxis)