Use dib-python to run package-installs using the provided python
version. Automatically detect the python version for our
package-installs-squash since that runs outside the chroot.
Change-Id: I926022bcf8cbcd81b051026ffd5d6477650045ad
Creating an element which we can use in #! lines to refer to either
python2 or python3 depending on what it available.
Change-Id: Ic47e18ad21c33ab9f0d11c04260a33725aeee814