systemc,tests,python: Updated testall.py to python3

Change-Id: I95fce9d71bf0af9cd76e8bf0dd353281cff8ed74
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/47022
Maintainer: Bobby R. Bruce <bbruce@ucdavis.edu>
Maintainer: Jason Lowe-Power <power.jg@gmail.com>
Reviewed-by: Jason Lowe-Power <power.jg@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>
(cherry picked from commit f9a941524febbea0143dd736ee8924f385ecf6f3)
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/47919
Reviewed-by: Bobby R. Bruce <bbruce@ucdavis.edu>
1 file changed