Py3 fix for geometric algebra non-zero-ness

pymbolic/geometric_algebra/__init__.py

@@ -897,9 +897,11 @@ class MultiVector(object):
 
         return result
 
-    def __nonzero__(self):
+    def __bool__(self):
         return bool(self.data)
 
+    __nonzero__ = __bool__
+
     def __eq__(self, other):
         other = _cast_or_ni(other, self.space)
         if other is NotImplemented: