py27-matplotlib @1.5.1_1: fails to import on OSX 10.7.5

[petrrr]

On an OS X 10.7.5 machine we get a somewhat strange error on import matplotlib.

Here the traceback:

>>> import matplotlib
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/matplotlib/__init__.py", line 1131, in <module>
    rcParams = rc_params()
  File "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/matplotlib/__init__.py", line 975, in rc_params
    return rc_params_from_file(fname, fail_on_error)
  File "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/matplotlib/__init__.py", line 1100, in rc_params_from_file
    config_from_file = _rc_params_in_file(fname, fail_on_error)
  File "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/matplotlib/__init__.py", line 1018, in _rc_params_in_file
    with _open_file_or_url(fname) as fd:
  File "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/contextlib.py", line 17, in __enter__
    return self.gen.next()
  File "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/matplotlib/__init__.py", line 1000, in _open_file_or_url
    encoding = locale.getdefaultlocale()[1]
  File "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/locale.py", line 543, in getdefaultlocale
    return _parse_localename(localename)
  File "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/locale.py", line 475, in _parse_localename
    raise ValueError, 'unknown locale: %s' % localename
ValueError: unknown locale: UTF-8
>>>

The strange thing here is that the locale looks reasonable, the same version just importa fine on other OS X versions. Also after downgrade to an earlier version (py27-matplotlib @1.4.3_0+cairo+tkinter), the import just works fine and the problem is gone.

The locale looks reasonable:

>>> import locale
>>> locale.getpreferredencoding()
'UTF-8'
)))

Any idea what's going on here?
Is this an upstream issue?