Check that reform has not been constructed when a formula or an input_variable is added
Check that reform has not been constructed when a formula or an input_variable is added

openfisca/openfisca-core,benjello/openfisca-core,benjello/openfisca-core,adrienpacifico/openfisca-core,sgmap/openfisca-core,openfisca/openfisca-core