Merge pull request #131 from l-johnston/fix_unitoperationerror_exception

fix UnitOperationError exception when the exponent is unyt_array or u…

unyt/array.py

@@ -1666,7 +1666,7 @@ def __array_ufunc__(self, ufunc, method, *inputs, **kwargs):
                     if u1.units.is_dimensionless:
                         pass
                     else:
-                        raise UnitOperationError(ufunc, u0, u1)
+                        raise UnitOperationError(ufunc, u0, u1.units)
                 if u1.shape == ():
                     u1 = float(u1)
                 else:

unyt/tests/test_unyt_array.py

@@ -63,7 +63,7 @@
 from unyt.unit_registry import UnitRegistry
 from unyt._on_demand_imports import _astropy, _h5py, _pint, NotAModule
 from unyt._physical_ratios import metallicity_sun, speed_of_light_cm_per_s
-from unyt import dimensions
+from unyt import dimensions, Unit
 
 
 def operate_and_compare(a, b, op, answer):
@@ -498,6 +498,12 @@ def test_power():
     with pytest.raises(UnitOperationError):
         np.power(cm_arr, unyt_quantity(3, "g"))
 
+    try:
+        np.power(cm_arr, unyt_quantity(3, "g"))
+    except UnitOperationError as err:
+        assert isinstance(err.unit1, Unit)
+        assert isinstance(err.unit2, Unit)
+
 
 def test_comparisons():
     """