Probably because of python2.7, which handles string differently than python3

See #78 for fix

After I updated the backup.py with suggested changes, I continue to receive following error.

Traceback (most recent call last):
File "./backup.py", line 466, in
main(sys.argv[1:])
File "./backup.py", line 223, in main
if system_service.data_centers_service().list(search='name=%s' % config.get_datacenter_name() )[0] is None:
File "/usr/lib64/python2.7/site-packages/ovirtsdk4/services.py", line 6507, in list
('search', search, str),
File "/usr/lib64/python2.7/site-packages/ovirtsdk4/service.py", line 191, in _check_types
raise TypeError(' '.join(messages))
TypeError: The 'search' parameter should be of type 'str', but it is of type 'unicode'.