pip now uses 2020 resolver by default.

domdfcoding · domdfcoding · commit e03942fce2a3 · 2021-01-18T09:37:01.000Z
diff --git a/tox.ini b/tox.ini
@@ -159,9 +159,7 @@ docstring-quotes = """
 count = True
 
 [testenv]
-setenv =
-    PIP_USE_FEATURE = 2020-resolver
-    PYTHONDEVMODE = 1
+setenv = PYTHONDEVMODE = 1
 deps = -r{toxinidir}/tests/requirements.txt
 extras = all
 commands =
