[rubygems/rubygems] Little refactor to avoid rubocop's false positive

Otherwise it detects duplicate methods here, because it doesn't see that
we are reopening the class in two different places.

ae3fb47f5f

test/rubygems/test_gem_commands_push_command.rb

@@ -27,25 +27,21 @@ class TestGemCommandsPushCommand < Gem::TestCase
 
     @cmd = Gem::Commands::PushCommand.new
 
-    class << Gem
+    singleton_gem_class.class_eval do
-
       alias_method :orig_latest_rubygems_version, :latest_rubygems_version
 
       def latest_rubygems_version
         Gem.rubygems_version
       end
-
     end
   end
 
   def teardown
     super
 
-    class << Gem
+    singleton_gem_class.class_eval do
-
       remove_method :latest_rubygems_version
       alias_method :latest_rubygems_version, :orig_latest_rubygems_version
-
     end
   end
 
@@ -404,4 +400,10 @@ class TestGemCommandsPushCommand < Gem::TestCase
     assert_equal '111111', @fetcher.last_request['OTP']
   end
 
+  private
+
+  def singleton_gem_class
+    class << Gem; self; end
+  end
+
 end