Update tox configuration for tox4

Author: amorison

tox.ini

@@ -1,17 +1,21 @@
 [tox]
-envlist = py37,py38,py39,py310,flake8,mypy
+envlist =
+    py37
+    py38
+    py39
+    py310
+    flake8
+    mypy
 skip_missing_interpreters = True
-skipsdist=True
 
 [testenv]
-usedevelop=True
 deps =
     pip>=20.2
     pytest>=6.0
     pytest-cov>=2.10
 commands =
     stagpy version
-    pytest --cov=stagpy --cov-report term-missing {posargs}
+    pytest --cov={envsitepackagesdir}/stagpy --cov-report term-missing {posargs}
 setenv = STAGPY_ISOLATED=True
 
 [testenv:flake8]