prioritize conda-forge over defaults channel

[RoyStegeman]

As discussed in #1284.

Relevant PR in binary-bootstrap: NNPDF/binary-bootstrap#4

[Zaharid]

I think the failure on mac has to do with numpy, given all the warnings we see. No idea why though.

[scarlehoff]

Hi @RoyStegeman, rebase master because something funny happened (my fault, modified something thinking it was just an example).

What I don’t understand is why does it stop 3.9 from running…

[Zaharid]

If I look at the current build failure for mac, I notice that we are pullinkg everything from conda-forge except for

    scipy:                         1.7.1-py38hf27351e_2                defaults                             

which seems to be the problem (no idea why that is happening).

Also at build time

    libarchive:      3.4.2-haa3ed63_0          defaults                             

which seems to not cause obvious problems.

Incidentally I wonder if disabling defaults alrogether would make thing simpler.

[RoyStegeman]

Incidentally I wonder if disabling defaults alrogether would make thing simpler.

Maybe, though I'm not sure if that's what we want to do in binary bootstrap and thus peoples local .condarc. Let me try what happens if we enforce a strict channel priority

[scarlehoff]

If I remember correctly in order to upload packages to conda forge you need to set strict channel priority so if it works it's a plus.