sage --notebook=export does not start

[egourgoulhon]

In Sage 8.1.rc0, the command sage --notebook=export (default for sage --notebook) fails with

[C 14:16:56.066 NotebookApp] Bad config encountered during initialization:
[C 14:16:56.066 NotebookApp] The 'nbserver_extensions' trait of a NotebookApp instance must be a dict, but a value of type 'list' (i.e. ['sagenb_export.nbextension']) was specified.

(see attached file for full log).

Both sage --notebook=jupyter and sage --notebook=sagenb are OK though.

This is on Ubuntu 16.04 and ahs been reported at
https://groups.google.com/d/msg/sage-release/7-eKF-xN0p0/z3T5zeMhAQAJ

NB: everything is OK with Sage 8.1.beta8, so the issue is most certainly due to a change introduced in Sage 8.1.beta9 or 8.1.rc0.

CC: @jdemeyer @kiwifb

Component: notebook

Author: Jeroen Demeyer

Branch/Commit: f8eef4e

Reviewer: Eric Gourgoulhon

Issue created by migration from https://trac.sagemath.org/ticket/24198

[egourgoulhon]

Log of "sage --notebook" command

[egourgoulhon]

comment:1

Attachment: sage_notebook.log

[egourgoulhon]

comment:2

It seems that the issue is related to #24064, which has been merged in Sage 8.1.beta9: in the discussion of that ticket, there is mention of nbserver_extensions, which appears in the error message.

[jdemeyer]

comment:3

Sorry for messing this up...

I usually run ./sage -n jupyter, so that is why I did not notice this.

[jdemeyer]

Author: Jeroen Demeyer

[jdemeyer]

Branch: u/jdemeyer/sage___notebook_export_does_not_start

[jdemeyer]

Commit: f8eef4e

[jdemeyer]

comment:5

The new format is a dict {module: enabled}.

---

New commits:

f8eef4e

Use correct format for nbserver_extensions

[egourgoulhon]

Reviewer: Eric Gourgoulhon

[egourgoulhon]

comment:6

Thanks for the fix! (I've just checked it on my computer).

[vbraun]

Changed branch from u/jdemeyer/sage___notebook_export_does_not_start to f8eef4e