While pbrx is nice and all, it's quite the divergence from how
the rest of the container ecosystem works. Switch to using
Dockerfile and the python-builder image.
Bind mount ld.so.cache into bwrap context
When using images based on the python:slim base image, python
is installed in /usr/local and the linker needs to know to look
in /usr/local/lib for shared libraries.
Depends-On: https://review.openstack.org/632187
Change-Id: I84f6dd2a8e3222f7807103dcbb61bdadedfdd22d
7fe0e780cf