debugger: Exit with error code on debugged error

When buildout encounter an error, program exists with error code 1, this
should also be the case when exiting from a debugger session when
running with -D option.

Closing #464

Fix most Deprecation and Resource warnings.

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Fix dependencies between zc.buildout and zc.recipe.egg after zc.recipe.egg 2.0.6 release

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Add 'allow-unknown-extras'

On Python 3, these made the build output very hard to read (e.g., https://travis-ci.org/buildout/buildout/jobs/394026829)

On Python 3.7, these could actually break the doctests.

Closing the files should get us closer to being able to pass the tests with PyPy.

Also add the required changes to zc.recipe.egg.

Fixes #457

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fix #295: temporary egg files are created as read only and can't be deleted with shutil on Windows.

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Compare using Distribution.parsed_version to account for normalization.

'python -m zc.buildout.tests TestEasyInstall'

Fixes #451.

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