[auth] pass `repo` instead of `vreg` to SessionManager and AuthenticationManager Those object actually need a repo object to connect and create new session object. They used to retrieve the repo object using ``vreg.config.repository()``. I'm trying to sanitise the initialisation stack and get ride of ``config.repository()``, a function that mix factory and cache. Retrieving the vreg from the repo is trivial (``repo.vreg``) so we now pass the repo object instead of the vreg.

from logilab.common.shellutils import generate_password
from cubicweb.server.utils import crypt_password

for user in rql('CWUser U WHERE U cw_source S, S name "system", U upassword P, U login L').entities():
    salt = user.upassword.getvalue()
    if crypt_password('', salt) == salt:
        passwd = generate_password()
        print 'setting random password for user %s' % user.login
        user.set_attributes(upassword=passwd)

commit()