memcached: wip disable patch not py3 compatible

TODO: use a slapos egg patch for py3 ... but do we still need this patch ?

product/ERP5Type/patches/memcache_client.py

@@ -2,6 +2,7 @@
 # Code based on python-memcached-1.53
 try:
     from memcache import _Host, Client, _Error
+    raise ImportError()
 except ImportError:
     pass
 else: