Bug 11437 jar packager: no error message but buttons disabled
20020314 on the 'jar manifest' wizard page, if you select to use existing manifest file there's no error message but next and finish are disabled user should be informed what to do to make the wizard happy
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/jarpackager/JarManifestWizardPage.java
*/
	protected void updatePageCompletion() {
		boolean pageComplete= isPageComplete();
		setPageComplete(pageComplete);
		if (pageComplete) {
			setErrorMessage(null);
		}
	}
	
	/**
	 * Creates a file resource handle for the file with the given workspace path.
	 * This method does not create the file resource; this is the responsibility
	 * of <code>createFile</code>.
	 *
	 * @param filePath the path of the file resource to create a handle for
	 * @return the new file resource handle
	 * @see #createFile
	 */
	protected IFile createFileHandle(IPath filePath) {
		if (filePath.isValidPath(filePath.toString()) && filePath.segmentCount() >= 2)
			return JavaPlugin.getWorkspace().getRoot().getFile(filePath);
		else
			return null;
	}
	/**
	 * Creates a new label with a bold font.
	 *
	 * @param parent the parent control
	 * @param text the label text
	 * @return the new label control