Specify ProtocolError
@@ -419,7 +419,7 @@ class Test(unittest.TestCase):
writer = png.Writer(width=4, height=1, greyscale=True)
o = BytesIO()
- self.assertRaises(png.Error,
+ self.assertRaises(png.ProtocolError,
writer.write,
o, [[1, 111, 222]])
