Informative error message when a test runs on an indexed parameter with values only specified after test date

[MaxGhenis]

See the IndexError in this test run. The trace shows some functions like check_homogeneous_nodes.

This test failed because the policy parameter was specified starting at 2021-05-12 but the test was for 2021. Changing the test to 2022 in PolicyEngine/policyengine-us@e5a134f resolved it.

Elsewhere I've seen this error message:

openfisca_core.errors.parameter_not_found_error.ParameterNotFoundError: The parameter 'fcc.ebb[categorical_eligibility]' was not found in the 2021-01-01 tax and benefit system.

I think it might not have shown up in this case because the parameter it's calling is smart-indexed, but I haven't made a MWE to check.