https://github.com/yaml/pyyaml/issues/695

--- PyYAML-6.0.orig/tox.ini
+++ PyYAML-6.0/tox.ini
@@ -0,0 +1,9 @@
+[tox]
+envlist = pypy3,py36,py37,py38,py39,py310
+
+[testenv]
+deps =
+    Cython
+commands =
+    python setup.py test
+passenv = PYYAML_TEST_GROUP