Issue with typing.AscyncGenerator for python 3.6.0

[esvhd]

Hi there,

I upgraded to nbconvert 6.0.7 from from 5.6.1 recently, so as part of that I installed nbclient 0.5.1.

python 3.6.0
typing 3.7.4.3
notebook 6.1.4

I'm running python 3.6.0 on this machine. After the upgraded I started getting these errors when I tried to start a notebook (500, internal error page):

#....
File "h:\anaconda3\lib\site-packages\nbclient\client.py", line447, in NotebookClient
  async def async_setup_kernel(self, **kwargs) -> t.AsyncGenerator:
AttributeError: module 'typing' has no attribute 'AsyncGenerator'

If I revert back to nbconvert 5.6.1 life is back to normal again, notebooks can be opened.

On another machine with python 3.7, I do not see this issue. This might be specifically related to python 3.6.0.

Unfortunately I couldn't upgrade the machine to 3.7 easily... Any idea how / why this was happening to 3.6.0?

Thanks.

[davidbrochart]

Hi @esvhd, thanks for opening an issue. I can reproduce the bug, but unfortunately fixing it in nbclient won't be enough since prompt-toolkit also has the issue, and they require python>=3.6.1 for that reason. Out of curiosity, what version of prompt-toolkit do you have?

[esvhd]

Hi @davidbrochart , thanks for taking the time to look at this. I'm using prompt-toolkit 2.0.4 in this environment.

[davidbrochart]

I see, I think they didn't have type checking yet in this version, so I guess that a fix in nbclient would work for you. Unfortunately I couldn't find a nice way to ignore the AsyncGenerator return type of async_setup_kernel depending on the python version.
#119 just removes the type. On the other hand, I'm not sure having this return type is of great value. So if nobody has an objection, I will go ahead and merge it.

[esvhd]

Thanks!

…

Sent from my iPad

On 2 Nov 2020, at 22:04, David Brochart ***@***.***> wrote:  I see, I think they didn't have type checking yet in this version, so I guess that a fix in nbclient would work for you. Unfortunately I couldn't find a nice way to ignore the AsyncGenerator return type of async_setup_kernel depending on the python version. #119 just removes the type. On the other hand, I'm not sure having this return type is of great value. So if nobody has an objection, I will go ahead and merge it. — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub, or unsubscribe.

[davidbrochart]

cc @MSeal @SylvainCorlay
We can either merge #119 which removes type checking for the return value of async_setup_kernel, or require python>=3.6.1 instead of currently python>=3.6.
Thoughts?

[rgbkrk]

I'd prefer we require python >= 3.6.1

[SylvainCorlay]

I'd prefer we require python >= 3.6.1

Same. 3.6.0 will also have outstanding security issues...

[davidbrochart]

Sorry @esvhd, we won't support python 3.6.0 anymore.