Merge pull request #985 from swails/bool_unit

Fix Python 3 support in unit package.

wrappers/python/simtk/unit/quantity.py

@@ -603,7 +603,7 @@ class Quantity(object):
         return bool(self._value)
 
     def __bool__(self):
-        return self.__nonzero__()
+        return bool(self._value)
 
     def __complex__(self):
         return Quantity(complex(self._value), self.unit)
@@ -818,7 +818,6 @@ def _is_string(x):
      except StopIteration:
          return False
 
-
 # run module directly for testing
 if __name__=='__main__':
     # Test the examples in the docstrings

wrappers/python/tests/TestUnits.py

@@ -448,7 +448,7 @@ class TestUnits(QuantityTestCase):
         self.assertAlmostEqualQuantities(n, 2.05834818672e-17 * u.mole)
         self.assertAlmostEqualQuantities(V, 5.2359833333333e-19 * u.meters**3)
         self.assertEqual(str(T), '310.0 K')
-        self.assertEqual(str(u.MOLAR_GAS_CONSTANT_R), '8.31447247122 J/(K mol)')
+        self.assertEqual(str(1*u.joules/u.kelvin/u.mole), '1 J/(K mol)')
         self.assertTrue(u.is_quantity(V))
         # Checks trouble with complicated unit conversion factors
         p1 = 1.0 * u.atmospheres