Use Python 3 for tests

Signed-off-by: Simon McVittie <smcv@debian.org>

Closes: #1463
Approved by: cgwalters

tests/bootloader-entries-crosscheck.py

@@ -1,4 +1,4 @@
-#!/usr/bin/python
+#!/usr/bin/python3
 #
 # Copyright (C) 2015 Red Hat
 #

tests/test-basic-user-only.sh

@@ -28,7 +28,7 @@ extra_basic_tests=5
 . $(dirname $0)/basic-test.sh
 
 $CMD_PREFIX ostree --version > version.yaml
-python -c 'import yaml; yaml.safe_load(open("version.yaml"))'
+python3 -c 'import yaml; yaml.safe_load(open("version.yaml"))'
 echo "ok yaml version"
 
 # Reset things so we don't inherit a lot of state from earlier tests

tests/test-concurrency.py

@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 # Copyright (C) 2017 Colin Walters <walters@verbum.org>
 #