The release of pip10 has shown up a few issues here
Firstly, pip10 now refuses to overwrite distutils installed packages,
which includes "python-virtualenv" on centos. History has shown us
that we want the packages installed and overwritten, to avoid the
packages coming back and messing things up.
Pre-install all the packages, then list the files in the packages with
"rpm" directly and remove them. This way pip is happy to install.
We need to take better account of the package names for this; on
Fedora things have switch to "python2-virtualenv" instead of
"python-virtualenv" and we can't use an alias to list the package
contents.
This also highlighted that python2-pip is in EPEL for centos, so
enable that when we install it. Make the epel element a no-op for non
centos/rhe distros.
There is a related change in recent fedora that python3 now installs
binaries into /usr/local/bin. There are commented swizzles in here to
ensure we retain the status quo of "pip" and "virtualenv" both being
python2 based, with the python3 versions being called explicitly
"pip3" and "virtualenv3" respectively.
Change-Id: I2ffdd9f615ae6b00428c17249e4f216774991b99
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
