OCL interpreter (and other diagnosis utilities) complains from ALE

[jdeantoni]

Bug description

when using OCL interpreter, for instance for diagnosis or query testing, an error show up in the console:

OCL: unstable global EPackage registry for 'http://eclipse.org/emf/ecoretools/ale/diagnostics'.
  (See https://bugs.eclipse.org/bugs/show_bug.cgi?id=544165#c14)
  Use org.eclipse.ocl.ecore.EcoreEnvironment.checkRegistry() to diagnose the offending contribution.
java.util.ConcurrentModificationException 

How to reproduce

Steps to reproduce the behavior:

not easy like many ConcurrentModificationException, but it seems to be more often when the acceleo interpreter is open

Screenshot

[dvojtise]

is this during a ale execution or a k3 or concurrent engine execution (ie. ALE conflict even if not currently used ) ?