Issue #25364: zipfile now works in threads disabled builds.
diff --git a/Lib/zipfile.py b/Lib/zipfile.py
index 85bdaa9..2bd1007 100644
--- a/Lib/zipfile.py
+++ b/Lib/zipfile.py
@@ -13,8 +13,11 @@
 import shutil
 import struct
 import binascii
-import threading
 
+try:
+    import threading
+except ImportError:
+    import dummy_threading as threading
 
 try:
     import zlib # We may need its compression method