Adopt `binderhub` #129

Job	Run time
Build tljh_repo2docker	1m 18s
Unit tests (3.8)	12m 8s
Integration tests (local)	10m 58s
Isolated tests	1m 11s
Unit tests (3.9)	16m 43s
Integration tests (binderhub)	25m 32s
Unit tests (3.10)	17m 13s
	1h 25m 3s

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