traffic_packets: fix SyntaxWarning: "is" with a literal

Python 3.8 adds this warning via https://bugs.python.org/issue34850:
  the "is" and "is not" operator sometimes is used with string and
  numerical literals. This code "works" on CPython by accident, because
  of caching on different levels (small integers and strings caches,
  interned strings, deduplicating constants at compile time). But it
  shouldn't work on other implementations, and can not work even on
  early or future CPython versions.

Reported-by: L. van Belle <belle@samba.org>
Signed-off-by: David Disseldorp <ddiss@samba.org>
Reviewed-by: Noel Power <noel.power@suse.com>
Autobuild-User(master): David Disseldorp <ddiss@samba.org>
Autobuild-Date(master): Mon Apr 27 12:19:59 UTC 2020 on sn-devel-184

diff --git a/python/samba/emulate/traffic_packets.py b/python/samba/emulate/traffic_packets.py
index a585482ccd4377f8231809fcc24c138982e877de..95c7465d2fc7216ed1337256450363fd603a2baf 100644 (file)
--- a/python/samba/emulate/traffic_packets.py
+++ b/python/samba/emulate/traffic_packets.py
@@ -336,7 +336,7 @@ def packet_ldap_3(packet, conversation, context):
 
     # try to guess the search expression (don't bother for base searches, as
     # they're only looking up a single object)
-    if (filter is None or filter is '') and scope != SCOPE_BASE:
+    if (filter is None or filter == '') and scope != SCOPE_BASE:
         filter = context.guess_search_filter(attrs, dn_sig, dn)
 
     samdb.search(dn,