bpo-40204: Pin Sphinx version to 2.3.1 in ``Doc/Makefile``. (GH-21141)
diff --git a/Doc/Makefile b/Doc/Makefile
index 05361f2..b8ca1ed 100644
--- a/Doc/Makefile
+++ b/Doc/Makefile
@@ -143,7 +143,7 @@
venv:
$(PYTHON) -m venv $(VENVDIR)
$(VENVDIR)/bin/python3 -m pip install -U pip setuptools
- $(VENVDIR)/bin/python3 -m pip install -U Sphinx==2.2.0 blurb python-docs-theme
+ $(VENVDIR)/bin/python3 -m pip install -U Sphinx==2.3.1 blurb python-docs-theme
@echo "The venv has been created in the $(VENVDIR) directory"
dist: