Calling set_value() for an attribute of ULong64 type raises TypeError exception. The problem occurs while providing an integer as a parameter. Appending the 'L' suffix (eg. 123L) solves the problem, but the solution is not supported in Python > 3.0 as the explicit long type exists no more.
Fixed in PyTango SVN trunk since revision #24232
Will become visible in next PyTango release 8.1.1
This was fixed in revision #24332, not #24232.