Getting setuptools/easy_install to play nicely with PYTHONPATH

Why do setuptools/easy_install .pth files not place nicely with PYTHONPATH, and how do I get them to play nicely, and keep the directories in my PYTHONPATH before those .pth shoves in the sys.path?

My current problem is I've created a package for our project, with the both PyYAML and PyCrypto as requirements.

  install_requires=["PyYAML",
                    "pycrypto >= 2.3"]

As we've been developing, we've installed PyYaml in the standard directory (/usr/lib64/python2.6/site-packages) with pip. We installed an older version of PyCrypto in there, then discovered we needed the newer one, which we installed under /opt/devtools/lib64/python2.6/site-packages. We've had already been setting our PYTHONPATH to read from /opt first, before /usr/lib64. And that all worked fine in development. When we ran, we got PyCrypto 2.3 from /opt, and PyYaml from /usr/lib64/....

But now, when I'm trying installing in a virtualenv, and when I run python setup.py develop, setuptools/distribute ends up adding /usr/lib64/python2.6/site-packages to the easy-install.pth, but not /opt/devtools/lib64/python2.6/site-packages. It's finding the right versions, as seen in the output:

Using 开发者_运维问答/home/s3447/projects/wsrs.git/emp_parsing
Searching for pycrypto==2.3
Best match: pycrypto 2.3
Adding pycrypto 2.3 to easy-install.pth file

Using /opt/wsrs-devtools/stow/pycrypto-2.3/lib64/python2.6/site-packages
Searching for PyYAML==3.10
Best match: PyYAML 3.10
Adding PyYAML 3.10 to easy-install.pth file

But not adding /opt/... to the easy-install.pth. (Only /usr/lib64... and the directory I ran setup.py in is added to the path.)

The end result is, although I setuptools thinks it was successfully, when I run my code, easy-install.pth decides it knows what I want better than I do, inserts itself before my PYTHONPATH, and I end up importing the wrong version of PyCrypto.

Two questions:

1. Why is setuptools inconsistent about which directories it adds to the .pth file? I would expect either both directories or neither directory to be installed.

2. Is there any way to get setuptools to not try to override my PYTHONPATH? Why was that even considered a good idea in the first place?

From what I understand of your question, this may be where to take your concerns about that: https://github.com/pypa/setuptools/issues/397

Sounds like others have had a similar problem. I could be wrong, I just use pip. I never use easy_install if I can help it.