function onDir( error ) {
			if ( error ) {
				debug( 'Error encountered when attempting to create an output directory: %s', error.message );
				return done( error );
			}
			debug( 'Output directory created.' );

			debug( 'Creating SVGs...' );
			next();
		}
Callback invoked upon attempting to create a destination directory.

@private
@param {(Error|null)} error - error object
@returns {void}