[!] Something wrong happened while importing the module modules.distances_1: cannot import name _ring Traceback (most recent call last):

File "./stf.py", line 8, in from stf.core.ui import console

File "/root/StratosphereTestingFramework-master/stf/core/ui/console.py", line 12, in  from stf.core.plugins import modules

File "/root/StratosphereTestingFramework-master/stf/core/plugins.py", line 40, in  modules = load_modules()

File "/root/StratosphereTestingFramework-master/stf/core/plugins.py", line 25, in load_modules module = import(module_name, globals(), locals(), ['dummy'], -1)

File "/root/StratosphereTestingFramework-master/modules/dns_parser.py", line 9, in  from stf.core.models import groupofgroupofmodels

File "/root/StratosphereTestingFramework-master/stf/core/models.py", line 1, in
import persistent

File "/usr/local/lib/python2.7/dist-packages/persistent/init.py", line 35, in
import persistent.timestamp as TimeStamp AttributeError: 'module' object has no attribute 'timestamp'