class Ferrum::NodeMovingError

def initialize(node, prev, current)
  @node = node
  @prev = prev
  @current = current
  super(message)
end

def message
  "#{@node.inspect} that you're trying to click is moving, hence " \
    "we cannot. Previously it was at #{@prev.inspect} but now at " \
    "#{@current.inspect}."
end