ImportError when importing Python module written in C in cloned Git repo

Question

I've just cloned the NiPy repository, but when I try to import nipy.algorithms.registration, I get the following error:

In [1]: import nipy.algorithms.registration
---------------------------------------------------------------------------
ImportError                               Traceback (most recent call last)
<ipython-input-1-17bae03bf7b5> in <module>()
----> 1 import nipy.algorithms.registration

/home/despo/dbliss/nipy/nipy/algorithms/__init__.py in <module>()
      7 __docformat__ = 'restructuredtext'
      8 
----> 9 import statistics
     10 import fwhm, interpolation, kernel_smooth, diagnostics
     11 

/home/despo/dbliss/nipy/nipy/algorithms/statistics/__init__.py in <module>()
      6 __docformat__ = 'restructuredtext'
      7 
----> 8 from . import intvol, rft, onesample, formula
      9 from ._quantile import _quantile as quantile, _median as median
     10 

ImportError: cannot import name intvol

I discovered that there are two files called intvol in the repository: intvol.c and intvol.pyx. What's going on?

SOLVED: See first comment below.