Fix annoy warning, when executing testcase.

activerecord/test/cases/helper.rb

@@ -22,6 +22,8 @@
 # Connect to the database
 ARTest.connect
 
+require 'support/mysql'
+
 # Quote "type" if it's a reserved word for the current connection.
 QUOTED_TYPE = ActiveRecord::Base.connection.quote_column_name('type')
 

activerecord/test/support/mysql.rb

@@ -0,0 +1,11 @@
+if defined?(Mysql)
+  class Mysql
+    class Error
+      # This monkey patch fixes annoy warning with mysql-2.8.1.gem when executing testcases.
+      def errno_with_fix_warnings
+        silence_warnings { errno_without_fix_warnings }
+      end
+      alias_method_chain :errno, :fix_warnings
+    end
+  end
+end