cannot start status gatherer

[kisiel]

Hi.

running tahoe 1.13.0 on ubuntu 16.04.5 LTS

I've created status gatherer with command tahoe create-stats-gatherer --hostname=HOSTNAME $BASEDIR my $BASEDIR contains now three files location port tahoe-stats-gatherer.tac

port is open

but when I do tahoe start $BASEDIR

I get following set of lines with error

2018-08-26T18:17:58+0200 [twisted.scripts._twistd_unix.UnixAppLogger#info] twistd 18.7.0 (/home/tahoe-user/venv/bin/python2 2.7.12) starting up.
2018-08-26T18:17:58+0200 [twisted.scripts._twistd_unix.UnixAppLogger#info] reactor class: twisted.internet.epollreactor.EPollReactor.
2018-08-26T18:17:58+0200 [-] Unhandled Error
	Traceback (most recent call last):
	  File "/home/tahoe-user/venv/local/lib/python2.7/site-packages/twisted/internet/base.py", line 428, in fireEvent
	    DeferredList(beforeResults).addCallback(self._continueFiring)
	  File "/home/tahoe-user/venv/local/lib/python2.7/site-packages/twisted/internet/defer.py", line 322, in addCallback
	    callbackKeywords=kw)
	  File "/home/tahoe-user/venv/local/lib/python2.7/site-packages/twisted/internet/defer.py", line 311, in addCallbacks
	    self._runCallbacks()
	  File "/home/tahoe-user/venv/local/lib/python2.7/site-packages/twisted/internet/defer.py", line 654, in _runCallbacks
	    current.result = callback(current.result, *args, **kw)
	--- <exception caught here> ---
	  File "/home/tahoe-user/venv/local/lib/python2.7/site-packages/twisted/internet/base.py", line 441, in _continueFiring
	    callable(*args, **kwargs)
	  File "/home/tahoe-user/venv/local/lib/python2.7/site-packages/allmydata/scripts/tahoe_daemonize.py", line 128, in start
	    srv = service_factory()
	  File "/home/tahoe-user/venv/local/lib/python2.7/site-packages/allmydata/scripts/tahoe_daemonize.py", line 119, in <lambda>
	    u"stats-gatherer": lambda: namedAny("allmydata.stats.StatsGathererService")(read_config(self.basedir, None), self.basedir, verbose=True),
	  File "/home/tahoe-user/venv/local/lib/python2.7/site-packages/allmydata/node.py", line 139, in read_config
	    portnumfile = os.path.join(basedir, portnumfile)
	  File "/home/tahoe-user/venv/lib/python2.7/posixpath.py", line 68, in join
	    if b.startswith('/'):
	exceptions.AttributeError: 'NoneType' object has no attribute 'startswith'

could you please help?