PyUnicode_CopyCharacters() fails if 'to' has more than 1 reference
diff --git a/Include/unicodeobject.h b/Include/unicodeobject.h
index 0b93276..99f54c3 100644
--- a/Include/unicodeobject.h
+++ b/Include/unicodeobject.h
@@ -522,7 +522,8 @@
character conversion when necessary and falls back to memcpy if possible.
Fail if 'to' is smaller than how_many or smaller than len(from)-from_start,
- or if kind(from[from_start:from_start+how_many]) > kind(to).
+ or if kind(from[from_start:from_start+how_many]) > kind(to), or if to has
+ more than 1 reference.
Return the number of written character, or return -1 and raise an exception
on error.