Fix flake8 violations

tests/test_util_nodes.py

@@ -10,14 +10,14 @@
 """
 from textwrap import dedent
 
+import pytest
+from docutils import frontend
 from docutils import nodes
 from docutils.parsers import rst
 from docutils.utils import new_document
-from docutils import frontend
 
-from sphinx.util.nodes import extract_messages, clean_astext
 from sphinx.transforms import ApplySourceWorkaround
-import pytest
+from sphinx.util.nodes import extract_messages, clean_astext
 
 
 def _transform(doctree):