Update Tornado

libs/tornado/wsgi.py

@@ -32,6 +32,7 @@ provides WSGI support in two ways:
 from __future__ import absolute_import, division, print_function, with_statement
 
 import sys
+from io import BytesIO
 import tornado
 
 from tornado.concurrent import Future
@@ -40,12 +41,8 @@ from tornado import httputil
 from tornado.log import access_log
 from tornado import web
 from tornado.escape import native_str
-from tornado.util import bytes_type, unicode_type
+from tornado.util import unicode_type
 
-try:
-    from io import BytesIO  # python 3
-except ImportError:
-    from cStringIO import StringIO as BytesIO  # python 2
 
 try:
     import urllib.parse as urllib_parse  # py3
@@ -58,7 +55,7 @@ except ImportError:
 # here to minimize the temptation to use them in non-wsgi contexts.
 if str is unicode_type:
     def to_wsgi_str(s):
-        assert isinstance(s, bytes_type)
+        assert isinstance(s, bytes)
         return s.decode('latin1')
 
     def from_wsgi_str(s):
@@ -66,7 +63,7 @@ if str is unicode_type:
         return s.encode('latin1')
 else:
     def to_wsgi_str(s):
-        assert isinstance(s, bytes_type)
+        assert isinstance(s, bytes)
         return s
 
     def from_wsgi_str(s):