From 6ea9003436e79163a865a0a30b6051f7811c1bd3 Mon Sep 17 00:00:00 2001
From: "Jason R. Coombs" <jaraco@jaraco.com>
Date: Sun, 29 Nov 2020 15:19:11 -0500
Subject: [PATCH] Declare MultiFormatResource.formatDefault as optional string
 for subclass overrides.

---
 src/allmydata/web/common_py3.py | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/src/allmydata/web/common_py3.py b/src/allmydata/web/common_py3.py
index 22f235790..080c24c19 100644
--- a/src/allmydata/web/common_py3.py
+++ b/src/allmydata/web/common_py3.py
@@ -4,6 +4,11 @@ Common utilities that are available from Python 3.
 Can eventually be merged back into allmydata.web.common.
 """
 
+try:
+    from typing import Optional
+except ImportError:
+    pass
+
 from twisted.web import resource, http
 
 from allmydata.util import abbreviate
@@ -47,7 +52,7 @@ class MultiFormatResource(resource.Resource, object):
     format if nothing else is given as the ``formatDefault``.
     """
     formatArgument = "t"
-    formatDefault = None
+    formatDefault = None  # type: Optional[str]
 
     def render(self, req):
         """