Fix broken flake8 configuration and flake8 errors which were hidden by this breakage. flake8 --filename options doesn't work as expected: * it's expected to be a shell pattern, using stdlib's fnmatch.fnmatch function internally. This funciton thinks that 'cubicweb/x.py' doesn't match 'cubicweb/x.py' (there must be a reason but that's not the point), hence no file was actually checked ; * as this is a list of pattern, each encountered file is checked against each pattern, leading to run time explosion. So maintain list of files to check in a separated file and give this list to flake8 using unix's xarg command.

from cubicweb.cwconfig import CubicWebConfiguration


def includeme(config):
    appid = config.registry.settings['cubicweb.instance']
    cwconfig = CubicWebConfiguration.config_for(appid)

    config.registry['cubicweb.config'] = cwconfig
    config.registry['cubicweb.repository'] = repo = cwconfig.repository()
    config.registry['cubicweb.registry'] = repo.vreg