Add debug print

skimage/util/tests/test_dtype.py

@@ -77,7 +77,7 @@ def test_downcast():
     with expected_warnings('Downcasting'):
         y = img_as_int(x)
     assert np.allclose(y, x.astype(np.int16))
-    assert y.dtype == np.uint16
+    assert y.dtype == np.uint16, y.dtype
 
 
 def test_float_out_of_range():