Add require 'rake'

to avoid uninitialized constant error

https://www.google.com/search?q=rake+hooks+%22uninitialized+constant+Rake%22&oq=rake+hooks+%22uninitialized+constant+Rake%22&aqs=chrome..69i57.5301j0j7&client=ubuntu-browser&sourceid=chrome&espv=2&es_sm=121&ie=UTF-8