--target doesn't work for namespace packages

When doing a local install of a namespace package, the .pth file doesn’t get picked up for some reason:

MAC-C08182:projects c08182$ mkdir targettest
MAC-C08182:projects c08182$ cd targettest/
MAC-C08182:targettest c08182$ pip install repoze.lru -t lib/
Downloading/unpacking repoze.lru
  Downloading repoze.lru-0.6.tar.gz
  Running setup.py (path:/private/var/folders/9w/_wt1czb57k9c5b0hgg6dfl2x7jbl85/T/pip_build_c08182/repoze.lru/setup.py) egg_info for package repoze.lru

Installing collected packages: repoze.lru
  Running setup.py install for repoze.lru

    Skipping installation of /var/folders/9w/_wt1czb57k9c5b0hgg6dfl2x7jbl85/T/tmp7uY1G8/lib/python/repoze/__init__.py (namespace package)
    Installing /var/folders/9w/_wt1czb57k9c5b0hgg6dfl2x7jbl85/T/tmp7uY1G8/lib/python/repoze.lru-0.6-py2.7-nspkg.pth
Successfully installed repoze.lru
Cleaning up...
MAC-C08182:targettest c08182$ PYTHONPATH=$(pwd)/lib
MAC-C08182:targettest c08182$ python
Python 2.7.7 |Anaconda 2.0.0 (x86_64)| (default, Jun  2 2014, 12:48:16) 
[GCC 4.0.1 (Apple Inc. build 5493)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
Anaconda is brought to you by Continuum Analytics.
Please check out: http://continuum.io/thanks and https://binstar.org
>>> import repoze.lru
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ImportError: No module named repoze.lru
>>> 
MAC-C08182:targettest c08182$ 

However, all necessary files are in fact installed in lib/:

MAC-C08182:targettest c08182$ cd lib/
MAC-C08182:lib c08182$ ls
repoze              repoze.lru-0.6-py2.7.egg-info
repoze.lru-0.6-py2.7-nspkg.pth
MAC-C08182:lib c08182$ 

And of course the whole procedure works just fine for non-namespace packages.

Thanks to @mmerickel for setting me straight on the source of the issue.

[webmaven]

@Ivoz site.addsitedir('lib') was exactly what I needed. Thanks!

[jaraco]

@JensTimmerman That’s an interesting idea. I agree, it’s a bit hostile to install packages into a --target and then they not be viable without some additional steps.

I’m not sure a warning is quite appropriate - as it may be the case that a tool invoking pip will be correcting for the condition as rwt does.

More importantly, though, this issue largely goes away with Python 3.3, so perhaps the best solution is just to work around it until you can port everything to Python 3.