Syseggrecipe

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- Nothing changed yet.

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- Added a little bit of extra logging. for 1.5's feature.
[reinout]

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- If a package isn't found, it sometimes only is a matter of a missing
``*.egg-info`` file. Like ubuntu, that misses the egg-info file for mapnik,
even though mapnik itself is installed.

We now attempt to import such a package (simply using the package name) and
use the directory it is installed in, if found. Note: the package name might
not be a valid import name. Support might have to be added for corner cases.
[reinout]

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- We now also find pip-installed packages (which end in
``.dist-info``). (Support added by Olivier Bornet, thanks!)

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- Fixed bug: ``%S`` instead of ``%s`` (lowercase) in a log message. You'd get
a ``ValueError: unsupported format character in recipe.py`` if you got hit
by the bug (which only happens in a corner case).

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- Using ``os.path.lexists()`` instead of ``os.path.exists()``, this one
returns True also if there's a symlink that leads nowhere. ``exists()``
follows the symlink so returns False for broken symlinks. In our case that
means that the broken symlink isn't removed so that the subsequent creation
of a new symlink fails as the filename is already in use. Fixes 3.