nbconvert broken in Jupyter notebooks of Sage 8.2.beta*

[Eric Gourgoulhon]

Hi,

After the upgrade to Jupyter 5.2.1 in Sage 8.2.beta0 (cf. #24168), the export of a notebook to another format seems broken. For instance, clicking on File -> Download as -> PDF via LaTeX leads to

500 : Internal Server Error

The error was:

Could not import nbconvert: No module named base

In the console from which "sage -n jupyter" is run, we get the error message:
 
[W 16:20:16.102 NotebookApp] 500 GET /nbconvert/pdf/Test.ipynb?download=true (127.0.0.1): Could not import nbconvert: No module named base
[E 16:20:16.105 NotebookApp] {
      "Accept-Language": "fr,fr-FR;q=0.8,en-US;q=0.5,en;q=0.3",
      "Accept-Encoding": "gzip, deflate",
      "Host": "localhost:8888",
      "Accept": "text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8",
      "User-Agent": "Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:57.0) Gecko/20100101 Firefox/57.0",
      "Connection": "keep-alive",
      "Referer": "http://localhost:8888/notebooks/Test.ipynb",
      "Cookie": "username-localhost-8888=\"2|1:0|10:1514992791|23:username-localhost-8888|44:NzgxYjgxZDY0ZmFhNDIyZDhhNjBhNTU3OWE4MzU4ODc=|ae01a5fbd715c538b6c695c0027f81f80ab579eda10271892f9fd65c94843604\"; username-localhost-8889=\"2|1:0|10:1514992623|23:username-localhost-8889|44:YzI3M2Y4ZjI1NDNmNDUyOWIwYjhiODFkMjBmNzBlZDU=|6a49b0751beebf75393a799c6517bda66f2d379eed82c30137667afedd1426aa\"; _xsrf=2|87e4c7b4|a9604e2304109e9eff0170f5c589f8f8|1514991468",
      "Upgrade-Insecure-Requests": "1"
    }
[E 16:20:16.105 NotebookApp] 500 GET /nbconvert/pdf/Test.ipynb?download=true (127.0.0.1) 70.20ms referer=http://localhost:8888/notebooks/Test.ipynb

On the same, computer, it is OK with Sage 8.1.

Eric.

[Eric Gourgoulhon]

Since I've got the same issue on a different computer (still running Ubuntu 16.04 though), I've opened a ticket:  #24484.

[David Corbin]

Can confirm that I am having the same issue on version 8.1 on macOS.