Do not allow a bare `thenAnswer()` #184

Job	Run time
Check with mypy	8s
Spellcheck with codespell	4s
Lint with flake8	5s
Run tests on Python 3.8 (ubuntu-latest)	19s
Run tests on Python 3.9 (ubuntu-latest)	11s
Run tests on Python 3.10 (ubuntu-latest)	10s
Run tests on Python 3.11 (ubuntu-latest)	8s
Run tests on Python 3.12 (ubuntu-latest)	10s
Run tests on Python 3.13 (ubuntu-latest)	19s
Run tests on Python 3.8 (macos-latest)	53s
Run tests on Python 3.9 (macos-latest)	29s
Run tests on Python 3.10 (macos-latest)	24s
Run tests on Python 3.11 (macos-latest)	11s
Run tests on Python 3.12 (macos-latest)	11s
Run tests on Python 3.13 (macos-latest)	9s
Run tests on Python 3.8 (windows-latest)	46s
Run tests on Python 3.9 (windows-latest)	28s
Run tests on Python 3.10 (windows-latest)	33s
Run tests on Python 3.11 (windows-latest)	42s
Run tests on Python 3.12 (windows-latest)	30s
Run tests on Python 3.13 (windows-latest)	1m 32s
Deploy to pypi	0s
	8m 22s

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