explicitly set encoding UTF-8 (#16107)

Default Ruby source file encoding changed in Ruby 2.0.0.
https://bugs.ruby-lang.org/issues/6679

git-svn-id: http://svn.redmine.org/redmine/trunk@12918 e93f8b46-1217-0410-a6f0-8f06a7374b81

test/integration/api_test/authentication_test.rb

@@ -41,8 +41,13 @@ class Redmine::ApiTest::AuthenticationTest < Redmine::ApiTest::Base
   end
 
   def test_invalid_utf8_credentials_should_not_trigger_an_error
+    invalid_utf8 = "\x82"
+    if invalid_utf8.respond_to?(:force_encoding)
+      invalid_utf8.force_encoding('UTF-8') 
+      assert !invalid_utf8.valid_encoding?
+    end
     assert_nothing_raised do
-      get '/users/current.xml', {}, credentials("\x82", "foo")
+      get '/users/current.xml', {}, credentials(invalid_utf8, "foo")
     end
   end