unittest2 error: TypeError: _recursive_repr() takes exactly 1 argument (0 given)

Question

I am trying to install openerp, which requires unittest2. I had to manually install it using pip (and I also tried easy_install) which seemed to work, but anything that touches it (including unit2) produces the following traceback:

    Traceback (most recent call last):
  File "/Library/Frameworks/Python.framework/Versions/2.7/bin/unit2", line 7, in <module>
    from unittest2.__main__ import main_
  File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/unittest2/__init__.py", line 40, in <module>
    from unittest2.collector import collector
  File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/unittest2/collector.py", line 3, in <module>
    from unittest2.loader import defaultTestLoader
  File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/unittest2/loader.py", line 13, in <module>
    from unittest2 import case, suite, util
  File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/unittest2/case.py", line 18, in <module>
    from unittest2 import result
  File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/unittest2/result.py", line 10, in <module>
    from unittest2.compatibility import wraps
  File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/unittest2/compatibility.py", line 143, in <module>
    class ChainMap(collections.MutableMapping):
  File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/unittest2/compatibility.py", line 190, in ChainMap
    @collections._recursive_repr()
TypeError: _recursive_repr() takes exactly 1 argument (0 given)

Trying to start the openerp server produces the same error. There doesn't seem to be any mention of this problem either here or in the googlesphere.

Any ideas?