CentOS 7 is the only distro we support currently that doesn't have
Python 3 installed in some form in the base images. For centos 7 add
an early install of it in the yum element so we can have all the
in-chroot scripts assume Python 3. There is only one package that
causes issues; yaml which comes from EPEL. Everywhere else it is a
base package, but we don't have a way to say "enable epel to install
this". Just hack it in, we don't want to go reworking the world for
CentOS 7 at this point.
Also add python3 and it's yaml library to the centos 8 path. This
brings in the "user" python3 in /urs/bin/python3 (the "system" python3
is already installed). Again, this just lets us assume
/usr/bin/python3 in scripts for all platforms.
package-installs is one of these things running python in the chroot,
and unfortunately we have elements that use it at 01- level in
pre-installd. Thus to make sure python3 is there nice and early, run
it at 0 level, but make sure it comes after yum/dnf update.
Change-Id: I088fc4284e889147ca9a375d4a159264cff53484
Currently we have all our elements and library files in a top-level
directory and install them into
<root>/share/diskimage-builder/[elements|lib] (where root is either /
or the root of a virtualenv).
The problem with this is that editable/development installs (pip -e)
do *not* install data_files. Thus we have no canonical location to
look for elements -- leading to the various odd things we do such as a
whole bunch of guessing at the top of disk-image-create and having a
special test-loader in tests/test_elements.py so we can run python
unit tests on those elements that have it.
data_files is really the wrong thing to use for what are essentially
assets of the program. data_files install works well for things like
config-files, init.d files or dropping documentation files.
By moving the elements under the diskimage_builder package, we always
know where they are relative to where we import from. In fact,
pkg_resources has an api for this which we wrap in the new
diskimage_builder/paths.py helper [1].
We use this helper to find the correct path in the couple of places we
need to find the base-elements dir, and for the paths to import the
library shell functions.
Elements such as svc-map and pkg-map include python unit-tests, which
we do not need tests/test_elements.py to special-case load any more.
They just get found automatically by the normal subunit loader.
I have a follow-on change (I69ca3d26fede0506a6353c077c69f735c8d84d28)
to move disk-image-create to a regular python entry-point.
Unfortunately, this has to move to work with setuptools. You'd think
a symlink under diskimage_builder/[elements|lib] would work, but it
doesn't.
[1] this API handles stuff like getting files out of .zip archive
modules, which we don't do. Essentially for us it's returning
__file__.
Change-Id: I5e3e3c97f385b1a4ff2031a161a55b231895df5b
