Add pytest plugin option to ignore unrecognized tags

[eslavich]

This is needed so that schemas examples can be tested before the schema's ExtensionType exists (or, tested when the package containing the ExtensionType isn't installed).

[codecov]

Codecov Report

Merging #771 into master will not change coverage.
The diff coverage is n/a.

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##           master     #771   +/-   ##
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  Coverage   93.82%   93.82%           
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  Files          43       43           
  Lines        4910     4910           
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  Hits         4607     4607           
  Misses        303      303

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[eslavich]

I'm going to merge this early so we can move forward with @shannnnnyyy's asdf-standard work, I'll address any comments in an additional PR.

[jdavies-st]

So it looks like this PR adds the plumbing for the pytest configuration and propagates it to the functions that need it. But where's the actual tag ignoring functionality implemented?

[eslavich]

So it looks like this PR adds the plumbing for the pytest configuration and propagates it to the functions that need it. But where's the actual tag ignoring functionality implemented?

Happily, that was already implemented in asdf, as a flag that is passed to the AsdfFile initializer. Once I propagate the flag to that point, the existing code takes over. The bit that ignores the warning if the flag is set is here:

https://github.com/spacetelescope/asdf/blob/master/asdf/yamlutil.py#L254

[jdavies-st]

Ah cool! I bet you were happy to find it already implemented! 😂