When an error occurs exporting Cucumber Tests using REST endpoint, the response should return a detailed message with the reason instead of a generic message

When Exporting Cucumber Tests using the REST endpoint, if an error occurs the response should contain the reason why the exportation failed instead of the generic message "Error occurred while exporting raven tests.".

An example is:

the user tries to export the Cucumber Tests using the filter ID of an other user, the response message could be for example "The filter with id '10000' belongs to another user"