def get_pxe_iso(env):
    """Return the disk image for the PXE boot iso."""
    name = env.config.require('ravello', 'pxe_iso')
    images = env.client.call('GET', '/diskImages')
    for image in images:
        if image['name'] == name:
            return image
    raise RuntimeError('PXE ISO `{}` not found.'.format(name))
