following Debian policies, we're shipping the 'sample_data' contents in /usr/share/matplotlib/sample_data/ but cbook.get_sample_data() looks up those files into the module directory.
I tried patching get_sample_data() to set root to the path above, but that caused all the examples using get_sample_data() to fail in generating the images during documentation build because at that time, /usr/share/matplotlib/sample_data/ is still not populate.
I've then decided to reintroduce examples.directory parameter: this way I'll be able to set the temporary path during build time, and the correct path once the package will be installed.
I'll start writing a patch right away, I'll post it here once ready.
I've opened #1479 (it's the first time I file a pull request, hope I did it correctly ;))
Thanks @sandrotosi. I'll close this in favour of #1479.