Trouble with hosting. What am I doing wrong?

(please quote your code)

It seems that you are passing args to the build process in using environment variables. Please make sure that you have done everything described here:

https://juliadocs.github.io/Documenter.jl/dev/man/hosting/

You may also want to pin to a specific version of Documenter in the relevant Project.toml, to make sure things don’t break if the interface changes.

Also, I like to look at the build setup of Documenter.jl itself to figure out the recommended way of doing things:

https://github.com/JuliaDocs/Documenter.jl/tree/master/docs