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* `EfdClient` now accepts non-UTC astropy.time.Time values (converting them, if necessary).
* Fix unit tests:
* Update ``casettes/*.yaml`` to include "path" as a returned value.
* Change fixture ``efd_client`` to an async context manager ``make_efd_client`` and call it explicitly.
* Import ``vcr`` explicitly and configure it so that it fails if the specified cassette files cannot be found or used.
This avoids two sources of mysterious failures.
* Consolidate a few tests to make it clearer that they are testing the same thing, and to reduce the number of cassette files needed.
* Run black and isort on the code.