tests: fix failures due to environment LANG settings (Issue #286) When the environment in which the tests are run dictates a non-English language (e.g. via LANG=de_DE.UTF-8), certain tests started to fail because formencode validation messages where translated in that language. A test failing this way is for example test_create_in_group_without_needed_permissions in kallithea/tests/functional/test_admin_repos.py . This is a regression of commit 3b29103657df (i18n: remove explicit formencode language setting), but in fact reverting it is not the right solution as there is no problem except during test execution. Instead, force the formencode language to 'empty' (meaning English) for test execution only. See also http://www.formencode.org/en/latest/i18n.html