89c89
< return _mem_classes.keys()
---
> return list(_mem_classes.keys())
218c218
< for i in xrange(nbr_mem_ctrls):
---
> for i in range(nbr_mem_ctrls):
236c236
< for i in xrange(len(subsystem.mem_ctrls)):
---
> for i in range(len(subsystem.mem_ctrls)):