':param cred_file: file of the configuration
snippet for authenticating against the test IMAP server(s).
:param cmd: command that will be executed to invoke offlineimap'

def __init__(self, cred_file=None, cmd='offlineimap'):

    OLITestLib.cred_file = cred_file
    if (not os.path.isfile(cred_file)):
        raise UserWarning(("Please    copy    'credentials.conf.sample'    to    '%s'    and    set    your    credentials    there." % cred_file))
    OLITestLib.cmd = cmd
