Install Instructions Sphinx Error for Debian Jessie based distributions

[anongoblin]

During install of Mediagoblin following stable media goblin release 0.90 the following error is received:
(Instructions to use)
​http://mediagoblin.readthedocs.io/en/stable/siteadmin/deploying.html
OS: Debian 8 / Devuan Jessie

Running Sphinx-1.6.5/setup.py -q bdist_egg --dist-dir
/tmp/easy_install-NMpkET/Sphinx-1.6.5/egg-dist-tmp-bQS0kd
error: Setup script exited with error in Sphinx setup command: Invalid environm$
python_version<"3.5"
Makefile:123: recipe for target 'bin/python' failed
make: * [bin/python] Error 1

I was able to work around this by
./bin/easy_install sphinx==1.6.1

1.6.1 seems to be the earliest sphinx to not have this error.

Note there is another issue here.

the first time you receive the error it is when you use this command:
./bootstrap.sh && ./configure && make

however the second time you run that command, the error does not appear. it only appears when you run the update/upgrade command listed on the deployment page. that command is:
git submodule update && ./bin/python setup.py develop --upgrade && ./bin gmg update

I would expect the error to appear under the bootstrap and configure commands.

[anongoblin]

Text was cut off by editor. It is Invalid environment marker: python_version<"3.5"

[Ben Sturmfels]

Closing now as the current Debian release is 10, so I don't think there's any value to investigating this further.