Cache wsgi property (fixes GH-677)

raven/contrib/django/middleware/wsgi.py

@@ -8,6 +8,7 @@ raven.contrib.django.middleware.wsgi
 from __future__ import absolute_import
 
 from raven.middleware import Sentry
+from raven.utils import memoize
 
 
 class Sentry(Sentry):
@@ -21,7 +22,7 @@ class Sentry(Sentry):
     def __init__(self, application):
         self.application = application
 
-    @property
+    @memoize
     def client(self):
         from raven.contrib.django.models import client
         return client