Hi,
I just installed firedrake globally with --global --sudo  options. I get this:
Successfully installed firedrake
Cleaning up...
Creating firedrake-update script.
Successfully installed Firedrake.

To upgrade firedrake, run firedrake/bin/firedrake-update

Now to test it:
osman@osman-desktop:~/FIREDRAKE$ python helmholtz.py
Traceback (most recent call last):
  File "helmholtz.py", line 47, in <module>
    from firedrake import *
  File "/usr/local/lib/python2.7/dist-packages/firedrake/__init__.py", line 3, in <module>
    from pyop2_utils import enable_mpi_prefork
ImportError: cannot import name enable_mpi_prefork

Have I missed anything?
python is  2.7, cython0.23

Thanks in advance
-osman