Revert "Manually merged from https://github.com/rubygems/rubygems/pull/2636"

31a6eaabc1 is obsoleted with
  https://github.com/rubygems/rubygems/pull/3820

lib/rubygems/mock_gem_ui.rb

@@ -6,27 +6,22 @@ require 'rubygems/user_interaction'
 # retrieval during tests.
 
 class Gem::MockGemUi < Gem::StreamUI
-
   ##
   # Raised when you haven't provided enough input to your MockGemUi
 
   class InputEOFError < RuntimeError
-
     def initialize(question)
       super "Out of input for MockGemUi on #{question.inspect}"
     end
-
   end
 
   class TermError < RuntimeError
-
     attr_reader :exit_code
 
     def initialize(exit_code)
       super
       @exit_code = exit_code
     end
-
   end
   class SystemExitException < RuntimeError; end
 
@@ -87,5 +82,4 @@ class Gem::MockGemUi < Gem::StreamUI
     raise TermError, status if status != 0
     raise SystemExitException
   end
-
 end