I just created a new Tomcat 7 application and the build finished without any error. There are couple of solutions:
- Create a new application and push the changes again. Just in case there was some issue with that gear.
- Create an empty file called force_clean_build inside your existing application .openshift/markers directory. Commit the file and push the changes. This will remove the .m2 repository and download all the dependencies and plugins again.