[gthumb] python scripts: use env to find python3

[Paolo Bacchilega <paobac src gnome org>]

commit c29b02f09a3355232a96596406ebd3d809cdd6be
Author: Paolo Bacchilega <paobac src gnome org>
Date:   Mon Oct 23 13:12:46 2017 +0200

    python scripts: use env to find python3

 gthumb/make-authors-tab.py |    2 +-
 gthumb/make-gthumb-h.py    |    2 +-
 po/make-potfiles-in.py     |    2 +-
 3 files changed, 3 insertions(+), 3 deletions(-)
---
diff --git a/gthumb/make-authors-tab.py b/gthumb/make-authors-tab.py
index a0e07f3..6fa5797 100755
--- a/gthumb/make-authors-tab.py
+++ b/gthumb/make-authors-tab.py
@@ -1,4 +1,4 @@
-#!/usr/bin/python3
+#!/usr/bin/env python3
 
 import sys
 import re
diff --git a/gthumb/make-gthumb-h.py b/gthumb/make-gthumb-h.py
index 986ced7..4f3ded9 100644
--- a/gthumb/make-gthumb-h.py
+++ b/gthumb/make-gthumb-h.py
@@ -1,4 +1,4 @@
-#!/usr/bin/python3
+#!/usr/bin/env python3
 
 import sys
 import re
diff --git a/po/make-potfiles-in.py b/po/make-potfiles-in.py
index e031af3..dffe4a3 100755
--- a/po/make-potfiles-in.py
+++ b/po/make-potfiles-in.py
@@ -1,4 +1,4 @@
-#!/usr/bin/python3
+#!/usr/bin/env python3
 
 import os
 import re