Exception when flushing xwiki cache (GroovyTemplateEngine.flushCache)

May be a problem with the recent groovy upgrade

Reproductibility :

• Call $xwiki.flushCache() in a wiki page
• or create a new class with the class editor, add a property, save the page

Exception :

java.lang.IncompatibleClassChangeError: Found interface groovy.lang.MetaClassRegistry, but class was expected
at com.xpn.xwiki.render.groovy.GroovyTemplateEngine.flushCache(GroovyTemplateEngine.java:334)
at com.xpn.xwiki.render.groovy.XWikiGroovyRenderer.flushCache(XWikiGroovyRenderer.java:66)
at com.xpn.xwiki.render.DefaultXWikiRenderingEngine.flushCache(DefaultXWikiRenderingEngine.java:353)
at com.xpn.xwiki.XWiki.flushCache(XWiki.java:2158)
at com.xpn.xwiki.XWiki.flushCache(XWiki.java:2133)
at com.xpn.xwiki.web.PropUpdateAction.propUpdate(PropUpdateAction.java:95)
at com.xpn.xwiki.web.SaveAndContinueAction.action(SaveAndContinueAction.java:59)
at com.xpn.xwiki.web.XWikiAction.execute(XWikiAction.java:147)
at org.apache.struts.action.RequestProcessor.processActionPerform(RequestProcessor.java:431)
at org.apache.struts.action.RequestProcessor.process(RequestProcessor.java:236)
at org.apache.struts.action.ActionServlet.process(ActionServlet.java:1196)
at org.apache.struts.action.ActionServlet.doPost(ActionServlet.java:432)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:709)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:269)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:188)
at com.xpn.xwiki.web.SetCharacterEncodingFilter.doFilter(SetCharacterEncodingFilter.java:117)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:215)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:188)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:213)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:174)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:117)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:108)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:151)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:874)
at org.apache.coyote.http11.Http11BaseProtocol$Http11ConnectionHandler.processConnection(Http11BaseProtocol.java:665)
at org.apache.tomcat.util.net.PoolTcpEndpoint.processSocket(PoolTcpEndpoint.java:528)
at org.apache.tomcat.util.net.LeaderFollowerWorkerThread.runIt(LeaderFollowerWorkerThread.java:81)
at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:689)
at java.lang.Thread.run(Thread.java:619)