tests: use appropriate Python (2 or 3) for json.tool

8 jobs for topic/default/python-variable in 3 minutes and 53 seconds (queued for 1 second)
Status Job ID Name Coverage
  Test
passed checks-py2 #115755

00:01:12

passed checks-py3 #115756

00:02:04

passed doc #115761

00:00:27

manual pytype #115754
allowed to fail manual
passed tests-py2-cext #115757

00:02:56

passed tests-py2-pure #115758

00:03:39

passed tests-py3-cext #115759

00:03:52

passed tests-py3-pure #115760

00:03:19