isException = function (node, currentNode, previousNode) {
  if (node.is('atrule')) {
    if (previousNode.contains('ident') && previousNode.first('ident').content === 'return') {
      return true;
    }
  }
  return false;
}
Determine if current node is an exception and end checks if it is
If we've picked up a return @rule ignore it

@param {Object} node - The original node
@param {object} currentNode - The current node block
@param {Object} previousNode - The node previous to our current node
@returns {bool} Whether or not the it is an exception