Get include string for list of dependent rpms to build package

def _get_deps(deps, tree_base, saltenv='base'):
    '''
    Get include string for list of dependent rpms to build package
    '''
    deps_list = ''
    if deps is None:
        return deps_list
    if not isinstance(deps, list):
        raise SaltInvocationError(
            '\'deps\' must be a Python list or comma-separated string'
        )
    for deprpm in deps:
        parsed = _urlparse(deprpm)
        depbase = os.path.basename(deprpm)
        dest = os.path.join(tree_base, depbase)
        if parsed.scheme:
            __salt__['cp.get_url'](deprpm, dest, saltenv=saltenv)
        else:
            shutil.copy(deprpm, dest)

        deps_list += ' {0}'.format(dest)

    return deps_list