Fix #6245: circular import error on importing SerializingHTMLBuilder

1 files changed, 9 insertions, 0 deletions

diff --git a/sphinx/builders/singlehtml.py b/sphinx/builders/singlehtml.py
index 1ee5a37b1..068d1c1c2 100644
--- a/sphinx/builders/singlehtml.py
+++ b/sphinx/builders/singlehtml.py
@@ -13,6 +13,7 @@ from os import path
 from docutils import nodes
 
 from sphinx.builders.html import StandaloneHTMLBuilder
+from sphinx.deprecation import RemovedInSphinx40Warning, deprecated_alias
 from sphinx.environment.adapters.toctree import TocTree
 from sphinx.locale import __
 from sphinx.util import logging
@@ -201,6 +202,14 @@ class SingleFileHTMLBuilder(StandaloneHTMLBuilder):
             self.handle_page('opensearch', {}, 'opensearch.xml', outfilename=fn)
 
 
+# for compatibility
+deprecated_alias('sphinx.builders.html',
+                 {
+                     'SingleFileHTMLBuilder': SingleFileHTMLBuilder,
+                 },
+                 RemovedInSphinx40Warning)
+
+
 def setup(app):
     # type: (Sphinx) -> Dict[str, Any]
     app.setup_extension('sphinx.builders.html')