Fatal error: entity_exportable_schema_fields in commerce_coupon.install

Got this error which was killing the site.

The entity module states

/**
 * Defines schema fields required for exportable entities.
 *
 * Warning: Do not call this function in your module's hook_schema()
 * implementation or update functions. It is not safe to call functions of
 * dependencies at this point. Instead of calling the function, just copy over
 * the content.
 * For more details see the issue http://drupal.org/node/1122812.
 */
function entity_exportable_schema_fields($module_col = 'module', $status_col = 'status') {}

The attached patch follows the code comment advice and moves this function into commerce_coupon.install fixing the error.