The function _get_user_name already exists in the base ckanext-harvest (https://github.com/ckan/ckanext-harvest/blob/9efb9f4ee579dbeef1bcb32fa52d5e33f9145d9e/ckanext/harvest/harvesters/base.py#L167) with an extended implementation, e.g. allows to customize the harvest user and uses the default fallback user.
Maybe there was a need in the past for this function in ckanext-dcat, but actually I see no longer the need to overwrite the function _get_user_name and restrict the functionality of the super function.
The function _get_user_name already exists in the base ckanext-harvest (https://github.com/ckan/ckanext-harvest/blob/9efb9f4ee579dbeef1bcb32fa52d5e33f9145d9e/ckanext/harvest/harvesters/base.py#L167) with an extended implementation, e.g. allows to customize the harvest user and uses the default fallback user. Maybe there was a need in the past for this function in ckanext-dcat, but actually I see no longer the need to overwrite the function _get_user_name and restrict the functionality of the super function.