Support docutils-0.18: Consume iterator of Element.traverse()

Since 0.18, Element.traverse() returns an iterator instead of
intermediate object.  As a result, the return value is always considered
as truthy value.  And it becomes fragile when the caller modifies the
doctree on the loop.

1 files changed, 1 insertions, 1 deletions

diff --git a/sphinx/transforms/post_transforms/code.py b/sphinx/transforms/post_transforms/code.py
index 52bca8e12..3c4c0ebab 100644
--- a/sphinx/transforms/post_transforms/code.py
+++ b/sphinx/transforms/post_transforms/code.py
@@ -42,7 +42,7 @@ class HighlightLanguageTransform(SphinxTransform):
                                            self.config.highlight_language)
         self.document.walkabout(visitor)
 
-        for node in self.document.traverse(addnodes.highlightlang):
+        for node in list(self.document.traverse(addnodes.highlightlang)):
             node.parent.remove(node)