jupyter-client 8.0.0 invalid json output

[kgartland-rstudio]

Our application executes the following command:
python -m jupyter kernelspec list --json

Since the 8.0.0 release today, we have been hitting an error. It looks like there's now some extra text before the JSON output so it doesn't parse properly. The following line was changed from a print output to a logger which seems to prefix the JSON with a log label and breaks JSON parsing.

https://github.com/jupyter/jupyter_client/pull/895/files#diff-8d595ac8be48da6c32e22dedb24097bae34a9ca54c6298f572ccab22db174fa7L68-R62

[blink1073]

Thanks for the report! Fix is coming in #921.