validate-yaml: use python rather than explicitly python3

The change here is to use '/usr/bin/env python' in validate-yaml.py
as all other tools/*.py do.

Additionally, change the Makefile to invoke validate-yaml.py with
the python that it has selected for other things (PYVER).

1 files changed, 1 insertions, 1 deletions

diff --git a/tools/validate-yaml.py b/tools/validate-yaml.py
index d8bbcfcb..a57ea847 100755
--- a/tools/validate-yaml.py
+++ b/tools/validate-yaml.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python3
+#!/usr/bin/env python
 
 """Try to read a YAML file and report any errors.
 """