Require older virtualenv for Python 3.6 in tox

frenzymadness · frenzymadness · commit 68a0a5f0bab6 · 2025-12-10T12:04:57.000+01:00
diff --git a/tox.ini b/tox.ini
@@ -1,4 +1,6 @@
 [tox]
+# Older virtualenv required for Python 3.6.
+requires = virtualenv<20.22.0
 envlist = black,mypy,py{36,39,310,311,312,313,314,315}
 isolated_build = True
 
