Fix DIB scripts python version

Now that DIB is python3 only we can remove a hack that made sure
scripts outside the chroot ran with the correct version of python.
This is necessary as python3 does not resolve symbolic links to the
binary like python2.x did, which causes element scripts to fail finding
modules when DIB was run from inside a venv.

This patch does the following:
1. Reverts 9c7b8d1714 which was the
   workaround for mixed python2/3 environments.
2. Updates the scripts to use "python3" instead of "python".

Change-Id: If2402bb02fc8a4778fa9434fa167ea1fafd87c28

diskimage_builder/elements/package-installs/bin/package-installs-squash

@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 
 # Copyright 2014 Hewlett-Packard Development Company, L.P.
 #

diskimage_builder/elements/svc-map/extra-data.d/10-merge-svc-map-files

@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 # Licensed under the Apache License, Version 2.0 (the "License"); you may
 # not use this file except in compliance with the License. You may obtain

diskimage_builder/lib/common-functions

@@ -241,14 +241,6 @@ function cleanup_image_dir () {
     rm -rf --one-file-system $TMP_IMAGE_DIR
 }
 
-function cleanup_temp_python_exec () {
-    if [ ! -z "$DIB_ORIGINAL_PATH" ]; then
-        export PATH=$DIB_ORIGINAL_PATH
-    fi
-    rm "$DIB_PYTHON_EXEC_TMP/python" || true
-    rmdir "$DIB_PYTHON_EXEC_TMP" || true
-}
-
 # Run a directory of hooks outside the target (that is, no chrooting).
 function run_d() {
     check_element

diskimage_builder/lib/disk-image-create

@@ -175,14 +175,6 @@ export DIB_DEBUG_TRACE
 export DIB_IMAGE_CACHE=${DIB_IMAGE_CACHE:-~/.cache/image-create}
 mkdir -p $DIB_IMAGE_CACHE
 
-# Setup a symbolic link to the correct python exec so that element
-# scripts running outside the chroot using "#!/usr/bin/env python" get
-# the right python version.
-export DIB_ORIGINAL_PATH=$PATH
-export DIB_PYTHON_EXEC_TMP=$(mktemp -d -t --tmpdir=$HOME .DIB_PYTHON_TMP.XXXXXXXX)
-ln -s "$DIB_PYTHON_EXEC" "$DIB_PYTHON_EXEC_TMP/python"
-export PATH=$DIB_PYTHON_EXEC_TMP:$DIB_ORIGINAL_PATH
-
 # We have a couple of critical sections (touching parts of the host
 # system or download images to common cache) that we use flock around.
 # Use this directory for lockfiles.
@@ -617,7 +609,6 @@ fi
 
 # Remove the leftovers, i.e. the temporary image directory.
 cleanup_image_dir
-cleanup_temp_python_exec
 
 # Restore fd 1&2 from the outfilter.py redirect back to the original
 # saved fd.  Note small hack that we can't really wait properly for

diskimage_builder/lib/img-functions

@@ -43,7 +43,6 @@ function cleanup () {
     dib-block-device umount
     cleanup_build_dir
     cleanup_image_dir
-    cleanup_temp_python_exec
 }
 
 # Helper function to run a command inside the chroot

diskimage_builder/lib/outfilter.py

@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 # Copyright 2014 Hewlett-Packard Development Company, L.P.
 #