Here is an example module not working.

Reproducible: Always

#######

salt:/srv/salt # ls _modules/sesceph.zip
_modules/sesceph.zip
salt:/srv/salt # unzip _modules/sesceph.zip
Archive:  _modules/sesceph.zip
   creating: sesceph/
  inflating: sesceph/__init__.pyc    
  inflating: sesceph/__init__.py     
salt:/srv/salt # cat  sesceph/__init__.py     
import logging

log = logging.getLogger(__name__)

__virtualname__ = 'sesceph'

__outputter__ = {
                'is_ok': 'is_ok'
                }

def is_ok():
    '''
    A function to make some spam with eggs!

    CLI Example::

        salt '*' test.spam eggs
    '''
    log.error('wibble')
    return {}


def __virtual__():
    return __virtualname__
salt:/srv/salt # salt '*'  saltutil.sync_modules
linux-2grp.fritz.box:
linux-geds.fritz.box:
    - modules.sesceph
salt-deb.yokel.org:
salt:/srv/salt # salt '*' sesceph.is_ok 
salt-deb.yokel.org:
    'sesceph.is_ok' is not available.
linux-2grp.fritz.box:
    'sesceph.is_ok' is not available.
linux-geds.fritz.box:
    'sesceph.is_ok' is not available.
ERROR: Minions returned with non-zero exit code