Fix lint error

7 jobs for master in 3 minutes and 12 seconds (queued for 44 seconds)
Status Job ID Name Coverage
  Syntax
passed #665
ruby
jruby_1.7

00:01:32

passed #666
ruby
jruby_9.1

00:00:55

passed #661
ruby
ruby_2.1

00:01:33

passed #662
ruby
ruby_2.2

00:02:15

passed #663
ruby
ruby_2.3

00:01:18

passed #664
ruby
ruby_2.4

00:00:56

 
  Linting
passed #667
ruby
rubocop

00:00:46