properly close resources

Fixes ``buildout.py:574: ResourceWarning: unclosed file <_io.TextIOWrapper...>```

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Fix race condition with working set not reflecting reality during integrity check.

may conflict with new eggs buildout is trying to install.

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Added sorting of working set used by zc.recipe.egg

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Install wheels via setuptools, fixes #425

Remove no longer existing winbot

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Fixed: could not install eggs with case issues

Setuptools 38.2.0 suddenly started supporting and downloading wheels.
.whl files would end up in the non-functioning and deprecated unpack_wheel().
The new default ('just use setuptools') works fine.

- If you use an older setuptools, setuptools won't download wheels and the new
  code won't be used.

- If you use buildout.wheel, you'll overwrite the unpacker anyway.

For instance when sdist file name and package name had different case.

Update implicit-parts.rst

miss {

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Use HTTPS for default PyPI index