nbsphinx error about pandoc version

[aaronmarkham]

This error is happening a lot.
Error:

  nbconvert.utils.pandoc.check_pandoc_version()
/home/ubuntu/nbsphinx/src/nbsphinx.py:1174: RuntimeWarning: You are using an unsupported version of pandoc (2.2.3.2).
Your version must be at least (1.12.1) but less than (2.0.0).
Refer to http://pandoc.org/installing.html.
Continuing with doubts...

I found that it is a known issue that has been patched in nbsphinx master. However, I have been unable to get the environment.yml file to use the following command to install master.

  - git+https://github.com/spatialaudio/nbsphinx.git@master

I tried a wide range of approaches to installing master, but I'm stuck with 0.4.2 or other errors that prevent a forced upgrade.