Fix tox v4 (#674)

Author: ssbarnea

tox.ini

@@ -1,7 +1,8 @@
 [tox]
+minversion = 4.0.16
 envlist=
   lint
-  py{36,37,38,39,310}
+  py
   doc
   packaging
 
@@ -13,7 +14,13 @@ commands=
     {envpython} -m mypy testinfra test
     {envpython} -m pytest {posargs:-v -n 4 --cov testinfra --cov-report xml --cov-report term test}
 usedevelop=True
-passenv=HOME TRAVIS DOCKER_CERT_PATH DOCKER_HOST DOCKER_TLS_VERIFY WSL_DISTRO_NAME
+passenv=
+    HOME
+    TRAVIS
+    DOCKER_CERT_PATH
+    DOCKER_HOST
+    DOCKER_TLS_VERIFY
+    WSL_DISTRO_NAME
 
 [testenv:lint]
 description = Performs linting tasks