XFAIL pytensor tests for uint64 data type

Author: Dhruvanshu-Joshi

tests/tensor/test_math.py

@@ -1394,6 +1394,7 @@ def _grad_list(self):
         # check_grad_max(data, eval_outputs(grad(max_and_argmax(n,
         # axis=1)[0], n)),axis=1)
 
+    @pytest.mark.xfail(reason="Fails due to #770")
     def test_uint(self):
         for dtype in ("uint8", "uint16", "uint32", "uint64"):
             itype = np.iinfo(dtype)