Upgrading to 0.3 for users running anaconda **CANNOT** be done properly using pip #1805

Quick summary

Updating via pip install --upgrade --no-deps astropy will leave users with a mix of files from 0.2.5 and 0.3

See https://gist.github.com/mwcraig/7523054 for steps to reproduce and the result...but a highlight of the result is that both of these imports succeed if astropy is updated this way:

from astropy.convolution import convolve, Gaussian1DKernel
from astropy.nddata.convolution.make_kernel import make_kernel 

Long version:

In the anaconda python distribution astropy is installed with the conda package manager. Upgrading via pip with either:

pip install --upgrade --no-deps astropy

or, the version I used when I forget that no-deps exists,

pip uninstall astropy
pip install astropy

will result in an installation of astropy that is a hybrid of 0.2.5 and 0.3. The reason, as far as I can tell, is that pip can't really uninstall 0.2.5 because it has no record what was installed; it sees only an egg-info file.

As a result, pip uninstall does not remove the astropy directory from site-packages. pip install puts 0.3 over that pre-existing directory; any files that existed in 0.2.5 but no longer exist in 0.3 remain because they have been neither deleted nor overwritten.

Fix:

Conda users should be told to update with

conda update astropy

which will be available whenever anaconda builds the package.

I have tested that this works properly (i.e. the number of tests discovered matches those in the installation issue worksheet and the tests pass with no errors) by building a conda package of 0.3rc1. You can test it in anaconda with:

conda update --channel http://conda.binstar.org/mwcraig astropy