# File lib/guard.rb, line 311
    def run_on_guards(scopes = {})
      if scope_guard = scopes[:guard]
        yield(scope_guard)
      else
        groups = scopes[:group] ? [scopes[:group]] : @groups
        groups.each do |group|
          catch :task_has_failed do
            guards(:group => group.name).each do |guard|
              yield(guard)
            end
          end
        end
      end
    end