Ah, didn't realize. Though I've been occasionally voicing an opinion that we shouldn't have setup_requires=['numpy'] at all. Although it's technically true, the way setup_requires works is problematic for large requirements like Numpy (ideally it would be the correct thing to do, but in practice it's problematic...)

Ok, so are you ok with just adding that link back into the astropy_helpers module, @embray ? That would remove the need to update setup.py here and in the affiliated packages/template (the latter being the more probelmatic one)

The only thing is, I'd rather keep it where it is now. What I could do (since this didn't actually intend to break anything) is the same thing I did with write_if_different, in that I'll go ahead and put
from .distutils_helpers import * in astropy_helpers.setup_helpers. But I'd rather change any imports that are using these (so keep this PR as is).

Basically a soft, pending deprecation/move.

Pushed a few changes to astropy_helpers to fix this.

ok, cool - will update this to the latest and remove the setup.py change

You misunderstood (or I was unclear). I suggested to not remove the setup.py change.

@embray oh, gotcha, but the fixes are so that affiliated packages are still ok. See the new commit.

👍 Thanks!

I think this needs to be updated now to incorporate astropy/astropy-helpers#112, so it can be used by #3166 .

Yes, and once this is merged I'll rebase #3166

Updated to lastest astropy-helpers. It seems to work, except now every call to setup.py yields a bunch of warnings (shown below). Everything seems to work, but the warnings suggest something isn't quite right... Any idea, @embray ?

astropy/erfa/setup_package.py:3: RuntimeWarning: Parent module 'astropy.erfa' not found while handling absolute import
  import os
astropy/erfa/setup_package.py:4: RuntimeWarning: Parent module 'astropy.erfa' not found while handling absolute import
  from distutils.extension import Extension
astropy/erfa/setup_package.py:6: RuntimeWarning: Parent module 'astropy.erfa' not found while handling absolute import
  from astropy_helpers import setup_helpers
astropy/table/setup_package.py:2: RuntimeWarning: Parent module 'astropy.table' not found while handling absolute import
  import os
astropy/table/setup_package.py:3: RuntimeWarning: Parent module 'astropy.table' not found while handling absolute import
  from distutils.extension import Extension
astropy/io/ascii/setup_package.py:3: RuntimeWarning: Parent module 'astropy.io.ascii' not found while handling absolute import
  import os
astropy/io/ascii/setup_package.py:4: RuntimeWarning: Parent module 'astropy.io.ascii' not found while handling absolute import
  from distutils.extension import Extension
astropy/io/fits/setup_package.py:3: RuntimeWarning: Parent module 'astropy.io.fits' not found while handling absolute import
  import os
astropy/io/fits/setup_package.py:5: RuntimeWarning: Parent module 'astropy.io.fits' not found while handling absolute import
  from distutils.core import Extension
astropy/io/fits/setup_package.py:6: RuntimeWarning: Parent module 'astropy.io.fits' not found while handling absolute import
  from glob import glob
astropy/io/fits/setup_package.py:8: RuntimeWarning: Parent module 'astropy.io.fits' not found while handling absolute import
  from astropy_helpers import setup_helpers
astropy/io/votable/setup_package.py:2: RuntimeWarning: Parent module 'astropy.io.votable' not found while handling absolute import
  from distutils.core import Extension
astropy/io/votable/setup_package.py:3: RuntimeWarning: Parent module 'astropy.io.votable' not found while handling absolute import
  from os.path import join
astropy/io/votable/setup_package.py:5: RuntimeWarning: Parent module 'astropy.io.votable' not found while handling absolute import
  from astropy_helpers import setup_helpers
astropy/utils/xml/setup_package.py:2: RuntimeWarning: Parent module 'astropy.utils.xml' not found while handling absolute import
  from distutils.core import Extension
astropy/utils/xml/setup_package.py:3: RuntimeWarning: Parent module 'astropy.utils.xml' not found while handling absolute import
  from os.path import join
astropy/utils/xml/setup_package.py:4: RuntimeWarning: Parent module 'astropy.utils.xml' not found while handling absolute import
  import sys
astropy/utils/xml/setup_package.py:6: RuntimeWarning: Parent module 'astropy.utils.xml' not found while handling absolute import
  from astropy_helpers import setup_helpers
astropy/vo/samp/setup_package.py:3: RuntimeWarning: Parent module 'astropy.vo.samp' not found while handling absolute import
  import os

That's bizarre. No, I don't see anything like that. I'll try to see if I can figure out what might cause such a warning though. What Python version?

I am seeing these warnings if I run python2.7 -Wall; @eteq do you have some setting on your Python to enable all warnings by default?

Testing a change that might fix this, though it's not really a big problem. I'm still curious why you saw it by default and not me.

Well, first attempt at a fix didn't do it, as it seems this is actually from deep in the import system. But it seems that adding from __future__ import absolute_import to the relevant modules will shush this.

The warnings do show up on Travis by the way, but only for Python 2.x, not 3.x. How shall we proceed, can we go ahead and merge this anyway since the warnings are harmless?

Yes, I'll submit a separate PR that will fix these warnings.

Ok, merging this and rebasing #3166

@embray - the from __future__ import absolute_import is probably a fine solution - that's one of the "standard" imports, anyway, for a lot of the regular code.

Note also that these are only for modules that have C code in them... Maybe this is an artifact of the builtins._ASTROPY_SETUP_ tricks or something? Not sure why that would have changed, though.

And I'm seeing what @astrofrog noted on Travis: py 2.7 by default shows this, while 3.x does not. As far as I know I don't have any atypical warning settings...

Yeah, this is just because prior to PEP 328 the default behavior for the import statement was to look for package-relative imports first, so if you're in astropy.io.fits and call import os it looks first for astropy.io.fits.os rather than looking from the top of sys.path. Because we're loading these setup_package modules without actually creating the package they belong to this warning occurs when it goes looking for the astropy.io.fits package to look in for the os module.

Enabling from __future__ import absolute_import disables the old functionality, so that these import statements are no longer treated as possible relative imports.

aah, gotcha, that makes sense. Thanks for the clarification!

I'm afraid I have a broken setup.py in the latest master, most probably due to this PR.

 python setup.py develop
Traceback (most recent call last):
  File "setup.py", line 21, in <module>
    from astropy_helpers.distutils_helpers import is_distutils_display_option
ImportError: No module named distutils_helpers

Is it something trivial I missed, or it's better to open a separate issue for it?

@bsipocz Not sure if this helps, but try running git submodule update.

@embray - Sadly it doesn't help locally. However the build starts when I test it on a linux server, but it fails with #3241

So, I think the problem was that I had an obsolete astropy_helpers repo in the same virtenv, and setup.py tried to import stuff from that one and not from the submodule.
The build is now working fine.