Error: Wheels are not supported with setuptools 38.2.0

[mgedmin]

Yesterday setuptools 38.2.0 came out with this interesting new feature:

• easy_install: add support for installing from wheels pypa/setuptools#1200: easy_install now support installing from wheels: they will be installed as standalone unzipped eggs.

Since then all my Jenkins jobs that run bin/buildout started failing with the following error

Getting distribution for 'zope.testrunner==4.7.0'.
Using unpack_wheel() shim over the deprecated wheel_to_egg() hook.
Please update your wheel extension implementation for one that installs a .whl
handler in zc.buildout.easy_install.UNPACKERS
While:
  Installing.
  Getting section test.
  Initializing section test.
  Installing recipe zc.recipe.testrunner.
  Getting distribution for 'zope.testrunner==4.7.0'.
Error: Wheels are not supported

Note: I'm not using buildout.wheel, and I've pinned the versions of every dependency and recipe, except for setuptools.

[reinout]

I have the same issue on jenkins (also no buildout.wheel). I haven't been able yet to get it to fail locally.

[reinout]

Setuptools suddenly unexpectedly downloads a .whl as it now supports that. Buildout sees it and wants to use some wheel-installer. Which isn't there. So it fails with the "Wheels are not supported" error message.

[reinout]

I did a quick test by hacking a local copy of buildout and changing this in easy_install.py:

UNPACKERS = {
    '.egg': unpack_egg,
    '.whl': unpack_egg,  # was: unpack_wheel
}

So now setuptools gets to install the wheel it downloaded in the first place.

Looks like it works like a charm. Quick test with numpy works, too.

[mgedmin]

To get it to fail locally, run bin/buildout buildout:eggs-directory=/tmp/new-empty-eggs-dir buildout:download-cache=.

[leorochael]

If we could feature-detect if setuptools supports wheel, we could switch at import time which unpack_x function to use for wheels.

[reinout]

I think I've found the easiest solution with #428

By default, the unpack_wheel() refuses to work, printing "wheels are not supported".
The new default is to let setuptools handle it.
The new default will only fire if a wheel is actually downloaded, which only happens when there's a new setuptools.

So.... ought to work!

[davisd50]

I just had to set the setuptools version in the virtual environment:

When creating a virtualenv:
virtualenv --no-setuptools myenv
. myenv/bin/activate
pip install setuptools=="38.1.0"

My build started working then.