Fixed TypeError and added documentation
diff --git a/docs/hazmat/primitives/padding.rst b/docs/hazmat/primitives/padding.rst
index 4092ac0..72378e1 100644
--- a/docs/hazmat/primitives/padding.rst
+++ b/docs/hazmat/primitives/padding.rst
@@ -70,6 +70,9 @@
:return bytes: Returns the data that was padded or unpadded.
:raises TypeError: Raised if data is not bytes.
:raises cryptography.exceptions.AlreadyFinalized: See :meth:`finalize`.
+ :raises TypeError: This exception is raised if ``data`` is not a binary
+ type. This is ``str`` in Python 2 and ``bytes`` in
+ Python 3.
.. method:: finalize()