Fixed "Address already in use" from liveserver.

Our WSGIServer rewrapped the socket errors from server_bind into
WSGIServerExceptions, which is used later on to provide nicer
error messages in runserver and used by the liveserver to see if
the port is already in use. But wrapping server_bind isn't enough since
it only binds to the socket, socket.listen (which is called from
server_activate) could also raise "Address already in use".

Instead of overriding server_activate too I chose to just catch socket
errors, which seems to make more sense anyways and should be more robust
against changes in wsgiref.

django/test/testcases.py

@@ -8,6 +8,7 @@ import json
 import os
 import posixpath
 import re
+import socket
 import sys
 import threading
 import unittest
@@ -21,8 +22,7 @@ from django.core.handlers.wsgi import get_path_info, WSGIHandler
 from django.core.management import call_command
 from django.core.management.color import no_style
 from django.core.management.commands import flush
-from django.core.servers.basehttp import (WSGIRequestHandler, WSGIServer,
-    WSGIServerException)
+from django.core.servers.basehttp import WSGIRequestHandler, WSGIServer
 from django.core.urlresolvers import clear_url_caches, set_urlconf
 from django.db import connection, connections, DEFAULT_DB_ALIAS, transaction
 from django.db.models.loading import cache
@@ -1028,10 +1028,9 @@ class LiveServerThread(threading.Thread):
                 try:
                     self.httpd = WSGIServer(
                         (self.host, port), QuietWSGIRequestHandler)
-                except WSGIServerException as e:
+                except socket.error as e:
                     if (index + 1 < len(self.possible_ports) and
-                        hasattr(e.args[0], 'errno') and
-                        e.args[0].errno == errno.EADDRINUSE):
+                        e.errno == errno.EADDRINUSE):
                         # This port is already in use, so we go on and try with
                         # the next one in the list.
                         continue