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On 24 September 2014 11:03, Robert Collins <robertc at robertcollins.net> wrote:

> So... FWIW I think I've got a cleaner implementation of namespaces
> *for our context* - it takes inspiration from the PEP-420 discussion
> and final design. It all started when Mike reported issues with testr
> to me.
>
> https://bugs.launchpad.net/oslo.db/+bug/1372250
>
> tl;dr: we should stop using pkg_resources style namespace packages and
> instead have an effectively empty oslo package that sets up the
> namespace, which all namespaced libraries would depend on. With a stub
> __init__ in local source trees that adds the site-packages path to
> itself automatically, and excluding that file in sdist, it should be
> entirely transparent to developers and packagers, with no file
> conflicts etc.
>
> This works with the existing pkg_resources namespace packages, lets us
> migrate away from the pkg_resources implementation one package at a
> time, and we don't need to rename any of the packages, and it works
> fine with uninstalled and install -e installed source trees.
>
> We need:
>  - a new olso package to introduce a common oslo/__init__.py
> (recommended in the pre-PEP420 world)
>  - a tiny pbr bugfix: https://review.openstack.org/123597
>  - and a patch like so to each project: https://review.openstack.org/123604
>
> I have such an olso package https://github.com/rbtcollins/oslo, if
> this sounds reasonable I will push up an infra patch to create it.

Doug raised on IRC a concern about system-site-packages.

I have tested this, and I can make it work, but I'm not sure its
needed: it is totally broken today:
----
# Put oslo.config in the system site and oslo.18n not yet installed
sudo apt-get install oslo.config
sudo apt-get remove oslo.i18n
# make a virtualenv with system site packages
mkvirtualenv --system-site-packages test-system-site
# install oslo.18n
pip install oslo.i18n
# now when I tested oslo.i18n doesn't depent on oslo.config, but lets be sure:
python -c 'import oslo.config; print oslo.config.__file__'
Traceback (most recent call last):
  File "<string>", line 1, in <module>
ImportError: No module named config

# Oh look! can't import oslo.config.
pip install oslo.db
...
python -c 'import oslo.config; print oslo.config.__file__'
/home/robertc/.virtualenvs/test-system-site/local/lib/python2.7/site-packages/oslo/config/__init__.pyc

# Now we need it, it got pulled in.
----

Now, as I say, I can fix this quite easily with a virtualenv aware pth
file, but since its broken today and AFAIK there isn't a bug open
about this, I think it will be fine.

When you install e.g. oslo.db which *does* depend on oslo.config,
oslo.config is being installed within the venv. I'm not sure if thats
strictly due to version constraints, or if its systemic.

So - I'd like to say that its a separate preexisting issue and we can
loop back and tackle it should it show up as a problem.

-Rob

-- 
Robert Collins <rbtcollins at hp.com>
Distinguished Technologist
HP Converged Cloud