cannot install about dpkt HOT 3 OPEN

after upgrading pyvisa from 1.4 to 1.5 

Traceback (most recent call last):
  File "setup.py", line 4, in <module>
    import dpkt
  File "c:\Users\fabio\Downloads\dpkt-1.8\dpkt\__init__.py", line 24, in <module>
    import ethernet
  File "c:\Users\fabio\Downloads\dpkt-1.8\dpkt\ethernet.py", line 128, in <module>
    __load_types()
  File "c:\Users\fabio\Downloads\dpkt-1.8\dpkt\ethernet.py", line 122, in __load_types
    mod = __import__(modname, g)
  File "c:\Users\fabio\Downloads\dpkt-1.8\dpkt\ip6.py", line 101, in <module>
    import ip
  File "c:\Users\fabio\Downloads\dpkt-1.8\dpkt\ip.py", line 258, in <module>
    __load_protos()
  File "c:\Users\fabio\Downloads\dpkt-1.8\dpkt\ip.py", line 255, in __load_protos
    IP.set_proto(v, getattr(mod, name.upper()))
AttributeError: 'module' object has no attribute 'VISA'

I see the same issue on Linux even with the latest PyVISA 1.6.

With the patches on "Issue 34:  dynamic module loading too careless", the 
problem fixed.