Fix test__socket_ex.

greentest/test__socket_ex.py

@@ -10,7 +10,7 @@ class TestClosedSocket(greentest.TestCase):
         sock = socket.socket()
         sock.close()
         try:
-            sock.send('a', timeout=1)
+            sock.send(b'a', timeout=1)
         except socket.error as ex:
             if ex.args[0] != 9:
                 raise

known_failures.py

@@ -91,7 +91,6 @@ test__refcount.py
 test__subprocess.py
 test__all__.py
 test__pywsgi.py
-test__socket_ex.py
 test__example_echoserver.py
 test__makefile_ref.py
 test__server_pywsgi.py