In general you should not rely on internal classes like "com.sun.org.apache.xml.internal.utils". Those may be changed or removed in later Java versions.
If you do not use that package explicitly in your code, maybe some of the dependencies of your module use it. You can exclude the import of packages in your bnd.bnd file like this:
Import-Package: !com.sun.org.apache.xml.internal.utils,*
Note the "*" at the end. That is required so that the bndtools still analyse all the other imports in your module.
