Update PSS verify signature code example.

Author: jelaiw

Doc/src/signature/pkcs1_pss.rst

@@ -21,14 +21,14 @@ The following example shows how the sender can use its own *private* key
 At the receiver side, the matching *public* RSA key is used to verify
 authenticity of the incoming message::
 
-    >>> key = RSA.import_key(open('pubkey.der').read())
+    >>> key = RSA.import_key(open('pubkey.der', 'rb').read())
     >>> h = SHA256.new(message)
     >>> verifier = pss.new(key)
     >>> try:
     >>>     verifier.verify(h, signature)
-    >>>     print "The signature is authentic."
-    >>> except (ValueError, TypeError):
-    >>>     print "The signature is not authentic."
+    >>>     print("The signature is authentic.")
+    >>> except (ValueError):
+    >>>     print("The signature is not authentic.")
 
 .. __: https://tools.ietf.org/html/rfc8017#section-8.1