[test] Replace logilab-common's with_tempdir by tempfile.TemporaryDirectory logilab-common's with_tempdir decorator, which is considered harmful (see https://www.logilab.org/ticket/8267966). Rely on backports.tempfile to provide TemporaryDirectory on Python 2. Re-export it in testlib module for convenience.

[check-manifest]
ignore =
  debian
  debian/*
  cubicweb.spec
  __pkginfo__.py