See #1839 (comment).

Version 1.2 of matplotlib includes this line which imports a header file from numpy that lives in numpy/npy_3kcompat.h. Well it turns out this file doesn't exist in version 1.4 of numpy, which we officially support.

This file does exist (note no 404 error) in version 1.5, though.

This does raise an interesting point: literally nobody is using numpy version 1.4, otherwise we would have received a bunch of complaints about build errors.

Time to purge the conditionals checking for numpy version 1.4.