[devtools] Make dependency on backports.tempfile (Python2) optional
The package may not be available in all systems (e.g. no Debian package exist
at the moment), and we should not crash with ImportError when importing
testlib from client code. Follow up on a6dc650bc230 where the dependency was
introduced.
[tox]
envlist = py27,py34,flake8
[testenv]
sitepackages = true
deps =
pytest
commands =
{envpython} -m pytest {posargs:test}
[testenv:flake8]
skip_install = true
whitelist_externals =
flake8
deps =
flake8
commands = flake8
[flake8]
exclude = cubicweb_%(cubename)s/migration/*,test/data/*,.tox/*