From b92a290632b12c18ffb678da62119ef74f73dc46 Mon Sep 17 00:00:00 2001
From: Mariusz Felisiak <felisiak.mariusz@gmail.com>
Date: Tue, 31 May 2022 07:05:58 +0200
Subject: [PATCH] Fixed #33753 -- Fixed docs build on Sphinx 5+.

Empty language is not supported anymore.
---
 docs/Makefile | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/docs/Makefile b/docs/Makefile
index 39f84ec0e3ff..2b4483053124 100644
--- a/docs/Makefile
+++ b/docs/Makefile
@@ -9,6 +9,11 @@ PAPER         ?=
 BUILDDIR      ?= _build
 LANGUAGE      ?=
 
+# Set the default language.
+ifndef LANGUAGE
+override LANGUAGE = en
+endif
+
 # Convert something like "en_US" to "en", because Sphinx does not recognize
 # underscores. Country codes should be passed using a dash, e.g. "pt-BR".
 LANGUAGEOPT = $(firstword $(subst _, ,$(LANGUAGE)))