In upgrading Express 11 to 11, pkg crashes on python

I'm running Solaris Express 11 (151a) and I wanted to upgrade it to the latest release of Solaris 11. The pkg command insisted I update it first, which I did. But now it no longer works with the following error

Caching catalogs ...Traceback (most recent call last):
  File "/usr/bin/pkg", line 5954, in handle_errors
    __ret = func(*args, **kwargs)
  File "/usr/bin/pkg", line 5918, in main_func
    runid=runid)
  File "/usr/bin/pkg", line 1366, in __api_alloc
    exact_match=exact_match, runid=runid)
  File "/usr/lib/python2.6/vendor-packages/pkg/client/api.py", line 344, in __init__
    runid=runid)
  File "/usr/lib/python2.6/vendor-packages/pkg/client/image.py", line 249, in __init__