Keywords not split by commas

[diazona]

When running tests/distribution/test_distribution_packages.py::TestExternalProject::test_keywords[pytest==7.3.0], setuptools-pyproject-migration generates a list of keywords split on commas, whereas the test support code does not split on commas. (Unless I got that backwards?) We should fix the test support code accordingly.

self = <test_distribution_packages.TestExternalProject object at 0x7f32b0cb92d0>
expected = StandardMetadata(name='pytest', version=<Version('7.3.0')>, description='pytest: simple powerful testing with Python',...are Development :: Testing', 'Topic :: Utilities'], keywords=['test,unittest'], scripts={}, gui_scripts={}, dynamic=[])
actual = StandardMetadata(name='pytest', version=<Version('7.3.0')>, description='pytest: simple powerful testing with Python',..., 'unittest'], scripts={'pytest': 'pytest:console_main', 'py.test': 'pytest:console_main'}, gui_scripts={}, dynamic=[])

    def test_keywords(self, expected: StandardMetadata, actual: StandardMetadata):
>       assert sorted(expected.keywords) == sorted(actual.keywords)
E       AssertionError: assert ['test,unittest'] == ['test', 'unittest']
E         At index 0 diff: 'test,unittest' != 'test'
E         Right contains one more item: 'unittest'
E         Full diff:
E         - ['test', 'unittest']
E         ?       - --
E         + ['test,unittest']

/home/diazona/programming/setuptools-pyproject-migration/tests/distribution/test_distribution_packages.py:167: AssertionError