tox: Use python3 within tempestenv
If3ff71dbe636ef98072b15f6599e6e641c222f30 had switched this to python3.6
but this breaks on distros where 3.6 is no longer provided by default,
such as Fedora.
Closes-Bug: #1861308
Change-Id: I0e0b9e88eea2499cb1b9727a7787c050c869c819
diff --git a/tox.ini b/tox.ini
index ff31fe8..401bbfe 100644
--- a/tox.ini
+++ b/tox.ini
@@ -5,7 +5,7 @@
ignore_basepython_conflict = True
[tempestenv]
-basepython = python3.6
+basepython = python3
sitepackages = False
setenv =
VIRTUAL_ENV={envdir}