code: @OverrideOnDemand
    protected boolean equalsLinkedException (@Nullable final Throwable t1, @Nullable final Throwable t2)
    {
      if (EqualsHelper.identityEqual (t1, t2))
        return true;
      if (t1 == null || t2 == null)
        return false;
      return t1.getClass ().equals (t2.getClass ()) && EqualsHelper.equals (t1.getMessage (), t2.getMessage ());
    }
docs: Overridable implementation of Throwable for the Linked exception field.
  This can be overridden to implement a different algorithm. This is
  customizable because there is no default way of comparing Exceptions in
  Java. If you override this method you must also override
  {@link #hashCodeLinkedException(HashCodeGenerator, Throwable)}!
  
  @param t1
  First Throwable. May be <code>null</code>.
  @param t2
  Second Throwable. May be <code>null</code>.
  @return <code>true</code> if they are equals (or both null)