
Traceback (most recent call last):

 "/usr/local/lib/python3.5/dist-packages/jupyterhub/app.py", line 1442, in start
yield service.start()

 "/usr/local/lib/python3.5/dist-packages/jupyterhub/services/service.py", line 228, in start
env['JUPYTERHUB_SERVICE_PREFIX'] = self.server.base_url
AttributeError: 'NoneType' object has no attribute 'base_url'
Traceback (most recent call last):


 "[...]/visidata/basesheet.py", line 154, in execCommand

escaped = super().execCommand2(cmd, vdglobals=vdglobals)


 "[...]/visidata/basesheet.py", line 66, in execCommand2

exec(code, vdglobals, LazyChainMap(vd, self))


 "options-sheet", line 1, in <module>

import math


 "[...]/visidata/extensible.py", line 60, in get_if_not

setattr(self, name, func(self))


 "[...]/visidata/metasheets.py", line 16, in optionsSheet

return OptionsSheet(sheet.name+"_options", source=sheet)


 "[...]/visidata/extensible.py", line 14, in newinit

oldinit(self, *args, **kwargs)


 "[...]/visidata/extensible.py", line 14, in newinit

oldinit(self, *args, **kwargs)


 "[...]/visidata/sheets.py", line 202, in __init__

self.setKeys(self.columns[:self.nKeys])
# initial list of key columns


 "[...]/visidata/sheets.py", line 512, in setKeys

vd.addUndo(undoAttrFunc(cols, 'keycol'))


 "[...]/visidata/undo.py", line 29, in addUndo

r.undofuncs.append((undofunc, args, kwargs))
AttributeError: 'NoneType' object has no attribute 'append'
