Can't print motion component of planar joint

[ahundt]

jPlan = rbd.Joint(rbd.Joint.Planar, True, 'jPlan')
jointResume(jPlan)
qParam = [np.pi/2., 0.2, 0.1]
print('translation:', np.array(jPlan.pose(qParam).translation().transpose()))
print('rotation:')
print(np.array(jPlan.pose(qParam).rotation()))
print('motion:', np.array(jPlan.motion([0.2, 0.5, -0.5])))
jPlan = rbd.Joint(rbd.Joint.Planar, True, 'jPlan')
jointResume(jPlan)
qParam = [np.pi/2., 0.2, 0.1]
print('translation:', np.array(jPlan.pose(qParam).translation().transpose()))
print('rotation:')
print(np.array(jPlan.pose(qParam).rotation()))
print('motion:', np.array(jPlan.motion([0.2, 0.5, -0.5])))
P = 3
A = 3
qZero = [0.0, 0.0, 0.0]
alphaZero = [0.0, 0.0, 0.0]
motion subspace =
[[0.0, 0.0, 0.0], [0.0, 0.0, 0.0], [1.0, 0.0, 0.0], [0.0, 1.0, 0.0], [0.0, 0.0, 1.0], [0.0, 0.0, 0.0]]
translation: [[-0.1  0.2  0. ]]
rotation:
[[ 6.123234e-17  1.000000e+00  0.000000e+00]
 [-1.000000e+00  6.123234e-17  0.000000e+00]
 [ 0.000000e+00  0.000000e+00  1.000000e+00]]
motion: 
---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-40-7c03fed93332> in <module>
      5 print('rotation:')
      6 print(np.array(jPlan.pose(qParam).rotation()))
----> 7 print('motion:', np.array(jPlan.motion([0.2, 0.5, -0.5])))

~/.local/lib/python3.5/site-packages/numpy/core/arrayprint.py in array_str(a, max_line_width, precision, suppress_small)
   1500         # for which indexing with () returns a 0d instead of a scalar by using
   1501         # ndarray's getindex. Also guard against recursive 0d object arrays.
-> 1502         return _guarded_str(np.ndarray.__getitem__(a, ()))
   1503 
   1504     return array2string(a, max_line_width, precision, suppress_small, ' ', "")

~/.local/lib/python3.5/site-packages/numpy/core/arrayprint.py in wrapper(self, *args, **kwargs)
    458             repr_running.add(key)
    459             try:
--> 460                 return f(self, *args, **kwargs)
    461             finally:
    462                 repr_running.discard(key)

TypeError: __str__ returned non-string (type bytes)