Returns the root folder of a vCenter.

    service_instance
        The Service Instance Object for which to obtain the root folder.

def get_root_folder(service_instance):
    '''
    Returns the root folder of a vCenter.

    service_instance
        The Service Instance Object for which to obtain the root folder.
    '''
    try:
        log.trace('Retrieving root folder')
        return service_instance.RetrieveContent().rootFolder
    except vim.fault.NoPermission as exc:
        log.exception(exc)
        raise salt.exceptions.VMwareApiError(
            'Not enough permissions. Required privilege: '
            '{}'.format(exc.privilegeId))
    except vim.fault.VimFault as exc:
        log.exception(exc)
        raise salt.exceptions.VMwareApiError(exc.msg)
    except vmodl.RuntimeFault as exc:
        log.exception(exc)
        raise salt.exceptions.VMwareRuntimeError(exc.msg)