I follow this tutorial: http://software.danielwatrous.com/wordpress-plugin-licensing-wicket-on-google-app-engine/. I add google app engine library to this project and then I
Possible solution is that, you should add appengine through app engine settings in eclipse and make sure that the sdk added by appengine setting appear before the one mentioned (i.e. /home/hudi/program/git/tournamenSystem/tournament-system/tournament-system-web/src/main/webapp/WEB-INF/lib/appengine-api-1.0-sdk-1.7.1.jar) in your build path. In this way your application would refer the appengine sdk from google plugin and not for the path which is giving error.
I had same issue where I was getting error for the sdk jar included from maven dependency.Hope it will help.