Issue #17047: remove doubled words added in 3.3
as reported by Serhiy Storchaka and Matthew Barnett.
diff --git a/mock.py b/mock.py
index 333bcbd..663a6d1 100644
--- a/mock.py
+++ b/mock.py
@@ -1586,7 +1586,7 @@
you pass in `create=True`, and the attribute doesn't exist, patch will
create the attribute for you when the patched function is called, and
delete it again afterwards. This is useful for writing tests against
- attributes that your production code creates at runtime. It is off by by
+ attributes that your production code creates at runtime. It is off by
default because it can be dangerous. With it switched on you can write
passing tests against APIs that don't actually exist!
