nose -> pytest

[pyrox0]

With your PR, here is a check list:

• Has test cases written?
• Has all code lines tested?
• Has make format been run?
• Please update CHANGELOG.yml(not CHANGELOG.rst)
• Has fair amount of documentation if your change is complex
• Agree on NEW BSD License for your contribution

This PR is similar to pyexcel/pyexcel-ods#45, where the test infrastructure has been moved from the deprecated nose test runner to the modern pytest test runner. The same tests run, and they all pass. I made the least possible code changes to get the tests to pass.

[chfw]

thank you very much for this migration! nose is not compatibile with python 3.10 onwards