buildout with z3c packages fails with import-error

[pylint-bot]

Originally reported by: Adam Groszer (BitBucket: agroszer, GitHub: @agroszer?)

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When running $ bin/pylint playground.form

The result is:

No config file found, using default configuration
************* Module playground.form
C:  1, 0: Missing module docstring (missing-docstring)
E:  7, 0: No name 'form' in module 'z3c' (no-name-in-module)
E:  7, 0: Unable to import 'z3c.form' (import-error)
E:  8, 0: No name 'form' in module 'z3c' (no-name-in-module)
E:  8, 0: Unable to import 'z3c.form.browser' (import-error)

But when you run bin/test the test passes, IOW z3c packages can be imported.

I created a repo to repro this:

https://github.com/agroszer/playground

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• Bitbucket: https://bitbucket.org/logilab/pylint/issue/687

[pylint-bot]

Original comment by Adam Groszer (BitBucket: agroszer, GitHub: @agroszer?):

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I guess I figured the z3c part.
It is bad namespace declaration, z3c packages use a variation of

#!python

try:
    # Declare this a namespace package if pkg_resources is available.
    import pkg_resources
    pkg_resources.declare_namespace('z3c')
except ImportError:
    pass

zope packages use

# this is a namespace package
try:
    import pkg_resources
    pkg_resources.declare_namespace(__name__)
except ImportError:
    import pkgutil
    __path__ = pkgutil.extend_path(__path__, __name__)

astroid has a workaround that checks for pkgutil.extend_path but not for pkg_resources.declare_namespace (in modutils.py def _module_file).
That's why z3c packages are import-error despite being on PYTHONPATH

Added https://bitbucket.org/logilab/astroid/issues/243/modutils-_module_file-ignores for astroid

[PCManticore]

This seems to work with the master branch. astroid got support for declare_namespace as well: https://github.com/PyCQA/astroid/blob/master/astroid/interpreter/_import/spec.py#L178