From 639fc2dd51808354a0b693b44666e9322c1dae8a Mon Sep 17 00:00:00 2001
From: Kovid Goyal <kovid@kovidgoyal.net>
Date: Sun, 27 Sep 2020 14:01:20 +0530
Subject: [PATCH] Add a bug reference for import not being thread safe

---
 src/calibre/utils/winreg/default_programs.py | 1 +
 1 file changed, 1 insertion(+)

diff --git a/src/calibre/utils/winreg/default_programs.py b/src/calibre/utils/winreg/default_programs.py
index be449c393a..b9b07db486 100644
--- a/src/calibre/utils/winreg/default_programs.py
+++ b/src/calibre/utils/winreg/default_programs.py
@@ -174,6 +174,7 @@ class Register(Thread):
         # make sure no imports happen in this thread as python's zipimport
         # machinery is not thread safe and main GUI importing is happening
         # in parallel
+        # https://bugs.python.org/issue38884
         try:
             self.do_register()
         except Exception: