if! -> unless, as code climate suggests

script/check_contributors_md

@@ -28,7 +28,7 @@ Please set it using
   end
 end
 
-if !system("grep", "-i", author, "CONTRIBUTORS.md") then
+unless system("grep", "-i", author, "CONTRIBUTORS.md") then
   abort %{
 Thanks for your contribution, #{author}!
 Please add your name and GitHub handle to the file CONTRIBUTORS.md,