Tox fails with no such option: --pre

[pytoxbot]

• Bitbucket: https://bitbucket.org/hpk42/tox/issue/126
• Originally reported by: cpcloud
• Originally created at: 2013-09-27T19:35:40.399

Offending line: https://bitbucket.org/hpk42/tox/src/f7f70c5ce0b49656688bb78f8b4f5a1a8f489d7f/tox/_config.py?at=default#cl-333

This option fails with pip==1.3.1.

[pytoxbot]

Original comment by @hpk42

Issue #139 was marked as a duplicate of this issue.

[pytoxbot]

Original comment by @hpk42

fix issue126: depend on virtualenv>=1.10.1 so that we can rely
(hopefully) on a pip version which supports --pre. (tox by default
uses to --pre). Note that tox also vendors an older virtualenv
for supporting python2.5 -- although the latter will be dropped at some point.

→ <<cset 7a16cd37007c>>

[pytoxbot]

Original comment by cpcloud

Upgrading my virtualenv to 1.10.1 "fixed" the problem. Not sure how many people are still using older versions.

[pytoxbot]

Original comment by @hpk42

Maybe tox just needs to depend on virtualenv>=1.10.1 given that it vendors an earlier virtualenv for python2.5?

[pytoxbot]

Original comment by @jenisys

I also stumbled over this problem several times.

It is related with virtualenv and its virtualenv_support package that stores copies of pip, setuptools (and distribute) installation packages. Therefore, it can happen that pip-1.3.1 is the installed pip version after you create a new virtual-environment (with tox). The current virtualenv-0.10.1 version normally installs pip-1.4.1 from its "virtualenv_support" directory (but note that virtualenv>=0.10 dropped support for python2.5).

In addition, there seem to be multiple copies of "virtualenv_support" sometimes. This seems to occur when you install/upgrade virtualenv once with pip and once with easy_install (setuptools). Therefore, a feasible workaround can be to remove "virtualenv" and all its "virtualenv_support" directories from the "site-packages" directory and reinstall "virtualenv" again.

Maybe the best way is that the configuration option "install_command" is not only a function of the python version but also of the pip version (that gets installed per default).

WORK-AROUNDS:

• Define "install_command = pip install {opts} {packages}" in "tox.ini"
• Ensure a clean virtualenv with pip-1.4.1 in its "virtualenv_support" directory (for Python>=2.6)