Error during load: Could not create the database table: validator/converter not found: u'scheming_multiple_choice_output'

I've just install XLoader on a clean install. While trying to push a CSV resource to the DataStore, I get the following error message:
Erreur : File "/usr/lib/ckan/default/src/ckanext-scheming/ckanext/scheming/validation.py", line 319, in get_validator_or_converter raise SchemingException('validator/converter not found: %r' % name) SchemingException("validator/converter not found: u'scheming_multiple_choice_output'",)

The log which resides under says at one point:
Error during load: Could not create the database table: validator/converter not found: u'scheming_multiple_choice_output'

Any idea on how to fix this?

Start with ckanext/scheming/validation.py at line 319 and reproduce the failure by pushing a CSV resource to the DataStore on a clean XLoader install. Trace how scheming_multiple_choice_output is looked up, then verify the load creates the database table without the validator/converter error.

Written by the indexing model from the issue text.