pip: pip 9.0.1 tries to build wheels for caching even when wheel is not installed

• Pip version: 9.0.1
• Python version: 3.5
• Operating system: debian unstable

Description:

User is reporting that buildbot is not installing under python3 unless wheel package is installed: https://github.com/buildbot/buildbot/issues/3495

What I’ve run:

Here are the commands I type:

$> pyvenv buildbot-sandbox
$> cd buildbot-sandbox/
$> . bin/activate
(buildbot-sandbox) $> pip install -U pip
Requirement already up-to-date: pip in ./lib/python3.5/site-packages
(buildbot-sandbox) $> pip --version
pip 9.0.1 from .../buildbot-sandbox/lib/python3.5/site-packages (python 3.5)
(buildbot-sandbox) $> pip install 'buildbot[bundle]'

I get the packages downloaded properly, but then most of the packages are failing like this (here the future package):

Building wheels for collected packages: future, Twisted, sqlalchemy, sqlalchemy-migrate, MarkupSafe, Tempita
  Running setup.py bdist_wheel for future ... error
  Complete output from command .../buildbot-sandbox/bin/python3.5 -u -c "import setuptools, tokenize;__file__='/tmp/pip-build-7r4e31_r/future/setup.py';f=getattr(tokenize, 'open', open)(__file__);code=f.read().replace('\r\n', '\n');f.close();exec(compile(code, __file__, 'exec'))" bdist_wheel -d /tmp/tmpdhk60rxdpip-wheel- --python-tag cp35:
  usage: -c [global_opts] cmd1 [cmd1_opts] [cmd2 [cmd2_opts] ...]
     or: -c --help [cmd1 cmd2 ...]
     or: -c --help-commands
     or: -c cmd --help

  error: invalid command 'bdist_wheel'

  ----------------------------------------
  Failed building wheel for future

Then, when I redo the process but I take care of installing wheel before installing buildbot, everything is fine. Note, I simply install the wheel package like this:

(buildbot-sandbox) $> pip install wheel