hgweb: adapt to socket._fileobject changes in Python 3

Differential Revision: https://phab.mercurial-scm.org/D2688

mercurial/hgweb/server.py

@@ -257,8 +257,8 b' class _httprequesthandlerssl(_httpreques'
 
     def setup(self):
         self.connection = self.request
-        self.rfile = socket._fileobject(self.request, "rb", self.rbufsize)
-        self.wfile = socket._fileobject(self.request, "wb", self.wbufsize)
+        self.rfile = self.request.makefile(r"rb", self.rbufsize)
+        self.wfile = self.request.makefile(r"wb", self.wbufsize)
 
 try:
     import threading