Make HTTPResponse.getHeaders() deterministic

Fixes #8.

src/zope/publisher/http.py

@@ -721,7 +721,7 @@ def getHeaders(self):
         result.append(
             ("X-Powered-By", "Zope (www.zope.org), Python (www.python.org)"))
 
-        for key, values in headers.items():
+        for key, values in sorted(headers.items(), key=lambda x: x[0].lower()):
             if key.lower() == key:
                 # only change non-literal header names
                 key = '-'.join([k.capitalize() for k in key.split('-')])

src/zope/publisher/tests/test_browserrequest.py

@@ -152,10 +152,10 @@ def testTraversalToItem(self):
         self.assertEqual(
             res,
             "Status: 200 Ok\r\n"
+            "X-Powered-By: Zope (www.zope.org), Python (www.python.org)\r\n"
             "Content-Length: 6\r\n"
             "Content-Type: text/plain;charset=utf-8\r\n"
             "X-Content-Type-Warning: guessed from content\r\n"
-            "X-Powered-By: Zope (www.zope.org), Python (www.python.org)\r\n"
             "\r\n"
             "'5', 6")
 

src/zope/publisher/tests/test_http.py

@@ -236,7 +236,6 @@ def _publisherResults(self, extra_env={}, body=b""):
         response = request.response
         publish(request, handle_errors=False)
         headers = response.getHeaders()
-        headers.sort()
         return (
             "Status: %s\r\n" % response.getStatusString()
             +
@@ -273,8 +272,8 @@ def testTraversalToItem(self):
         self.assertEqual(
             res,
             "Status: 200 Ok\r\n"
-            "Content-Length: 6\r\n"
             "X-Powered-By: Zope (www.zope.org), Python (www.python.org)\r\n"
+            "Content-Length: 6\r\n"
             "\r\n"
             "'5', 6")