Fix tox4 erros

tox.ini started failing with Tox4 which had some
incompatible changes. This change adresses the issues.

Change-Id: Iacdc525b2411b4e256c4d8b742975d8043dd2825
diff --git a/tox.ini b/tox.ini
index 153ebbf..454b8df 100644
--- a/tox.ini
+++ b/tox.ini
@@ -1,7 +1,6 @@
 [tox]
 minversion = 3.1.1
 envlist = py3,pypy,pep8
-skipsdist = True
 
 [testenv]
 basepython = python3