Workspaces Manager does not work when installed with Extension Manager

• apt-get install xwiki-enterprise-tomcat6-mysql in version 4.2
• imported appropriate XE 4.2 xar file
• grant all privileges on . to xwiki@localhost [...]
• set xwiki.virtual and xwiki.virtual.usepath to 1 in xwiki.cfg
• installed "XWiki Platform - Wiki Manager - UI 4.2" via extension manager
  • success with warning: 'installed but not valid' (see screenshot no 1)
• imported appropriate XEM 4.2 xar file
• installed wiki template
• installed workspace template

==> success till here

• goto 'create new workspace'
• got warning:
  "The Workspace Manager java component is not installed. This page will not work properly. Make sure that the file 'wiki30-components-workspace-manager-<version>.jar' is present under the 'webapps/xwiki/WEB-INF/lib/' folder.
  "

= workaround =

installed following jars manually:

• workspace component
• xwiki manager plugin
• application manager plugin

see bash script:

cd /usr/lib/xwiki/WEB-INF/lib/
wget http://nexus.xwiki.org/[...]/xwiki-platform-workspace-api-4.2.jar
wget http://maven.xwiki.org/[...]/xwiki-platform-wiki-manager-api-4.2.jar
wget http://maven.xwiki.org/[...]/xwiki-platform-application-manager-api-4.2.jar
/etc/init.d/tomcat6 restart

= caveats =

• more 'insalled but not valid' messages in extension manager after workaround