def _make_pr(source_repo, source_branch, base_ref, base_url=''):
    """Create a PR JSON object."""
    return {
        'head': {
            'repo': {
                'full_name': source_repo,
            },
            'ref': source_branch,
        },
        'base': {
            'ref': base_ref,
            'repo': {
                'clone_url': base_url,
            },
        },
    }