fix build docs

diff --git a/docs/requirements.txt b/docs/requirements.txt
index db9ffbf5b6154511d0c6c4c70f416a8d1a526ad2..30bc11d90f636b9ad49832bd23e79296a0d0f8db 100644 (file)
--- a/docs/requirements.txt
+++ b/docs/requirements.txt
@@ -6,3 +6,4 @@ sphinxcontrib-fulltoc
 guzzle_sphinx_theme
 docutils!=0.15,<0.18
 jinja2<3.1.0
+alabaster==0.7.13 # higher versions require Sphinx>3.4