Incompatibility with py3k filter() function

[Dalton Barreto]

In py3k, different from py2, the filter() function returns an filter object, not a list or tuple, etc.

With this, plugnplay breaks here:

plugnplay/plugnplay/__init__.py

Line 87 in 8cbe725

 def normalize_path(path): 

Traceback (most recent call last):
  File "/home/daltonmatos/projetos/plugnplay/tests/common.py", line 17, in test_normalize_path_complex
    self.assertEquals('pnp.some.module.path', normalize_path('/some/module/path'))
  File "/home/daltonmatos/projetos/plugnplay/plugnplay/__init__.py", line 92, in normalize_path
    return '.'.join([PNP_SYS_MODULES_PREFIX] + parts)
TypeError: can only concatenate list (not "filter") to list