# HG changeset patch
# User Pierre-Yves David <pierre-yves.david@ens-lyon.org>
# Date 2017-03-15 22:11:04
# Node ID 2daeab02b4b13b4d4829c216fd0db39e9733ba0b
# Parent  d4645ae6ba1592a2dc6bc2e82036dd4d090b3a49

hgweb: explicitly tests for None

Changeset 7dafa8d0e006 removed the mutable default value, but did not explicitly
tested for None. Such implicit testing can introduce semantic and performance
issue. We move to an explicit testing for None as recommended by PEP8:

https://www.python.org/dev/peps/pep-0008/#programming-recommendations

diff --git a/mercurial/hgweb/common.py b/mercurial/hgweb/common.py
--- a/mercurial/hgweb/common.py
+++ b/mercurial/hgweb/common.py
@@ -96,7 +96,9 @@ class ErrorResponse(Exception):
             message = _statusmessage(code)
         Exception.__init__(self, message)
         self.code = code
-        self.headers = headers or []
+        if headers is None:
+            headers = []
+        self.headers = headers
 
 class continuereader(object):
     def __init__(self, f, write):