Ensure we don't accidentally work on invalid rrules #107

Job	Run time
Build distribution packages	19s
Cross-arch tests with nox (arm64, ubuntu-20.04, 3.11, pytest_min)	34m 26s
Test with nox (ubuntu-20.04, 3.11, ci_checks_max)	53s
Test with nox (ubuntu-20.04, 3.11, pytest_min)	47s
Test documentation website generation	0s
Cross-arch tests with nox (arm64, ubuntu-20.04, 3.11, pytest_max)	34m 27s
Test package installation in different architectures	2m 33s
Test with nox	1s
Cross-arch tests with nox	1s
Publish documentation website to GitHub pages	0s
Create GitHub release	0s
Publish packages to PyPI	0s
	1h 13m 27s

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