[Cython] Cythonize silently ignores nonexistent files

[Kevin Norris]

Is this behavior intentional?

    >>> from Cython.Build import cythonize
    >>> cythonize('/this/file/doesnt/exist.pyx')
    []

It would be *really* nice if Cython would raise an exception (or
something) in this case.  I just spent 20 minutes trying to puzzle out
Cython/Setuptools compatibility when the actual problem was staring me
in the face.

--
Kevin Norris