Bug 118516 [DataBinding] Asserts should provide meaningful messages
Currently we use JDK Assert in various places in the code. However, if an assert fails, there often is no indication of why it failed or what the assert failure means without looking at the code indicated by the stack trace. It would be nicer if we would log exceptions or throw RuntimeExceptions with useful error messages instead.
bundles/org.eclipse.core.databinding.beans/src/org/eclipse/core/internal/databinding/internal/beans/ListenerSupport.java
private Set elementsListenedTo = new HashSet();
	
	private PropertyChangeListener listener;
	private String propertyName;
	/**
	 * Constructs a new instance.
	 * 
	 * @param listener is the callback that will be called
	 * 		when a <code>PropertyChangeEvent</code> is fired on any
	 * 		of the target objects.  Will only receive change events 
	 * 		when the provided <code>propertyName</code> changes.
	 * @param propertyName
	 */
	public ListenerSupport(final PropertyChangeListener listener,
			final String propertyName) {
		Assert.isNotNull(listener);
		Assert.isNotNull(propertyName);
		this.propertyName = propertyName;
		this.listener = new PropertyChangeListener() {
			public void propertyChange(PropertyChangeEvent evt) {
				if (propertyName.equals(evt.getPropertyName())) {