class RuboCop::Cop::Style::RedundantFileExtensionInRequire

Checks for the presence of superfluous ‘.rb` extension in the filename provided to `require` and `require_relative`.

NOTE: If the extension is omitted, Ruby tries adding ‘.rb’, ‘.so’,

and so on to the name until found. If the file named cannot be found,
a `LoadError` will be raised.
There is an edge case where `foo.so` file is loaded instead of a `LoadError`
if `foo.so` file exists when `require 'foo.rb'` will be changed to `require 'foo'`,
but that seems harmless.

@example

# bad
require 'foo.rb'
require_relative '../foo.rb'

# good
require 'foo'
require 'foo.so'
require_relative '../foo'
require_relative '../foo.so'