[gitg] flatpak: Use python3 on post install

[Alberto Fanjul <albfan src gnome org>]

commit c3cd73778a71f2037210b06f3c9cc4b69270b037
Author: Alberto Fanjul <albertofanjul gmail com>
Date:   Fri Jun 28 19:42:58 2019 +0200

    flatpak: Use python3 on post install

 meson_post_install.py | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/meson_post_install.py b/meson_post_install.py
old mode 100644
new mode 100755
index 967e9e2b..69d13785
--- a/meson_post_install.py
+++ b/meson_post_install.py
@@ -27,7 +27,7 @@ if not os.environ.get('DESTDIR'):
 
   if sys.argv[2] == 'python':
     print('Byte-compiling python modules...')
-    subprocess.call(['python', '-m', 'compileall', '-f', '-q', sys.argv[3]])
+    subprocess.call(['python3', '-m', 'compileall', '-f', '-q', sys.argv[3]])
 
     print('Byte-compiling python modules (optimized versions) ...')
-    subprocess.call(['python', '-O', '-m', 'compileall', '-f', '-q', sys.argv[3]])
+    subprocess.call(['python3', '-O', '-m', 'compileall', '-f', '-q', sys.argv[3]])