Issue #20791: copy.copy() now doesn't make a copy when the input is a bytes object.  Initial patch by Peter Otten.
diff --git a/Lib/copy.py b/Lib/copy.py
index d26bcdb..bb8840e 100644
--- a/Lib/copy.py
+++ b/Lib/copy.py
@@ -110,7 +110,7 @@
 def _copy_immutable(x):
     return x
 for t in (type(None), int, float, bool, str, tuple,
-          frozenset, type, range,
+          bytes, frozenset, type, range,
           types.BuiltinFunctionType, type(Ellipsis),
           types.FunctionType, weakref.ref):
     d[t] = _copy_immutable