[Distutils] Buildout 2 and system packages

[Lele Gaifax]

Jim Fulton <jim at zope.com> writes:

> I'm very happy, finally, to have released buildout 2.0.0.

I'm happy too, congrats to everybody contributed!

> Much has changed from buildout 1:
>
>   http://pypi.python.org/pypi/zc.buildout/2.0.0#id3

* Buildout no-longer tries to provide full or partial isolation from
  system Python installations. If you want isolation, use buildout with
  virtualenv, or use a clean build of Python to begin with.

Ok, I think I'm hitting this, trying to update one project: one of its
scripts fails with the following traceback::

    $ .../bin/initialize_cpi_db --development src/cpi/development.ini
    Traceback (most recent call last):
      File ".../bin/initialize_cpi_db", line 51, in <module>
        import cpi.scripts.initializedb
      File ".../src/cpi/cpi/__init__.py", line 10, in <module>
        from pyramid.config import Configurator
      File ".../eggs/pyramid-1.4-py2.7.egg/pyramid/config/__init__.py", line 21, in <module>
        from pyramid.authorization import ACLAuthorizationPolicy
      File ".../eggs/pyramid-1.4-py2.7.egg/pyramid/authorization.py", line 9, in <module>
        from pyramid.security import (
      File ".../eggs/pyramid-1.4-py2.7.egg/pyramid/security.py", line 12, in <module>
        from pyramid.threadlocal import get_current_registry
      File ".../eggs/pyramid-1.4-py2.7.egg/pyramid/threadlocal.py", line 3, in <module>
        from pyramid.registry import global_registry
      File ".../eggs/pyramid-1.4-py2.7.egg/pyramid/registry.py", line 5, in <module>
        from zope.interface.registry import Components
    ImportError: No module named registry

And the problem is that, even if I explicitly said it needs the
zope.interface egg, and pinned it to version 4.0.3, the script sees the
system wide zope.interface installed by the underlying Ubuntu host::

    $ cat .../bin/initialize_cpi_db
    #!/usr/bin/python

    import sys
    sys.path[0:0] = [
      '.../eggs/SQLAlchemy-0.8.0b2-py2.7-linux-i686.egg',
      '.../src/cpi',
      '.../eggs/docutils-0.10-py2.7.egg',
      '.../eggs/logutils-0.3.3-py2.7.egg',
      '.../src/metapensiero.extjs.desktop/src',
      '.../src/metapensiero.sphinx.patchdb/src',
      '.../src/metapensiero.sqlalchemy.proxy/src',
      '.../eggs/psycopg2-2.4.6-py2.7-linux-i686.egg',
      '.../eggs/pyramid-1.4-py2.7.egg',
      '.../eggs/pyramid_beaker-0.7-py2.7.egg',
      '.../eggs/pyramid_mailer-0.10-py2.7.egg',
      '.../eggs/rst2pdf-0.93.dev-py2.7.egg',
      '.../eggs/simplejson-3.0.7-py2.7-linux-i686.egg',
      '.../eggs/Babel-1.0dev_r661-py2.7.egg',
      '.../eggs/Sphinx-1.1.3-py2.7.egg',
      '.../eggs/coverage-3.5.1-py2.7-linux-i686.egg',
      '.../eggs/lingua-1.4-py2.7.egg',
      '.../eggs/nose-1.2.1-py2.7.egg',
      '.../eggs/nose_progressive-1.4-py2.7.egg',
      '.../eggs/yuicompressor-2.4.7-py2.7.egg',
      '.../eggs/blessings-1.3-py2.7.egg',
      '.../eggs/xlwt-0.7.4-py2.7.egg',
      '.../eggs/xlrd-0.8.0-py2.7.egg',
      '.../eggs/polib-1.0.2-py2.7.egg',
      '.../eggs/Jinja2-2.6-py2.7.egg',
      '.../eggs/Pygments-1.5-py2.7.egg',
      '.../eggs/pdfrw-0.1-py2.7.egg',
      '/usr/lib/python2.7/dist-packages',
      '.../eggs/repoze.sendmail-3.2-py2.7.egg',
      '.../eggs/Beaker-1.6.4-py2.7.egg',
      '.../eggs/PasteDeploy-1.5.0-py2.7.egg',
      '.../eggs/translationstring-1.1-py2.7.egg',
      '.../eggs/venusian-1.0a6-py2.7.egg',
      '.../eggs/zope.deprecation-4.0.0-py2.7.egg',
      '.../eggs/zope.interface-4.0.3-py2.7-linux-i686.egg',
      '.../eggs/repoze.lru-0.6-py2.7.egg',
      '.../eggs/WebOb-1.2.3-py2.7.egg',
      '.../eggs/Mako-0.7.2-py2.7.egg',
      '.../eggs/Chameleon-2.11-py2.7.egg',
      '.../eggs/zope.sqlalchemy-0.7.1-py2.7.egg',
      '.../eggs/waitress-0.8.1-py2.7.egg',
      '.../eggs/transaction-1.3.0-py2.7.egg',
      '.../eggs/pyramid_tm-0.5-py2.7.egg',
      '.../eggs/MarkupSafe-0.15-py2.7-linux-i686.egg',
      ]

    import cpi.scripts.initializedb

    if __name__ == '__main__':
        sys.exit(cpi.scripts.initializedb.main())

You may notice the “/usr/lib/python2.7/dist-packages” right in the
middle of the generated load path::

    $ bin/python

    >>> import zope.interface
    >>> print(zope.interface)
    <module 'zope.interface' from '/usr/lib/python2.7/dist-packages/zope/interface/__init__.pyc'>

I do understand that the documentation says “use virtualenv” to fix the
issue, but I'm curious about the position of the “dist-packages” in the
list: 

1) why does it ends in the middle? 
2) is (the position) controllable/explicitly determinable in some way?

Thanks a lot,
bye, lele.
-- 
nickname: Lele Gaifax | Quando vivrò di quello che ho pensato ieri
real: Emanuele Gaifas | comincerò ad aver paura di chi mi copia.
lele at metapensiero.it  |                 -- Fortunato Depero, 1929.