Use `py_require()` #411

Job	Run time
ubuntu-latest, tf-default, R-release	5m 1s
windows-latest, tf-default, R-release	7m 51s
macOS-latest, tf-default, R-release	2m 34s
windows-latest, tf-default, R-oldrel	9m 22s
macOS-latest, tf-default, R-oldrel	2m 40s
ubuntu-latest, tf-default, R-oldrel	3m 49s
ubuntu-latest, tf-default, R-oldrel-1	3m 35s
ubuntu-latest, tf-default, R-oldrel-2	4m 42s
ubuntu-latest, tf-default, R-oldrel-3	4m 2s
ubuntu-latest, tf-2.17, R-release	3m 38s
ubuntu-latest, tf-2.16, R-release	4m 8s
ubuntu-latest, tf-2.15, R-release	3m 38s
ubuntu-latest, tf-2.14, R-release	3m 54s
ubuntu-latest, tf-2.13, R-release	3m 20s
ubuntu-latest, tf-2.12, R-release	4m 41s
	1h 6m 55s

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