tools: use python3 (#274)

* tools: use python3

Switch tools/ to use python3 instead of python.  At minimum this
fixes building deb on python3 only releases like Focal. Applied
via shell commands:

 $ grep 'usr/bin/.*python' tools/* 2>/dev/null | \
     grep -v python3 | awk -F':' '{print $1}' | \
     xargs -i sed -i -e '0,/python/s/python/python3/' {}

* Use /usr/bin/env python3 to be virtualenv friendly

1 files changed, 1 insertions, 1 deletions

diff --git a/tools/read-version b/tools/read-version
index 92e9fc96..02c90643 100755
--- a/tools/read-version
+++ b/tools/read-version
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 
 import os
 import json