Config-resolver

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Fixed
~~~~~

* If a config-file contains any parser errors, that file is skipped while
logging a "critical" error. This prevents crashes caused by broken configs.

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Fixed
~~~~~

* The deprecation warning about the *filename* argument stated the exact
opposite to what it should have said :( This is fixed now

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Fixed
~~~~~

* Don't emit deprecation warnings when the code is called as expected.

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Fixed
~~~~~

* Fixed a regression introduced by 4.3.2

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Fixed
~~~~~

* Replace hand-crafted code with ``stack_level`` information for deprecation
warnings

-------------------

Fixed
~~~~~

* Fixed type hints
* Arguments ``require_load`` and ``version`` are no longer ignored in
``get_config``