So I conveyed the issue somewhat poorly, apologies. We want to use the conda environment.yml to do two things. One is be our rtd build keystone. Two is be our way for developers who want to build the docs locally to do so with as few steps as possible. Something like `../.` was working locally as a way of getting whatever is currently installed to be relative to the location of the file. (see [this commit](https://github.com/jupyter/nbconvert/commit/f03ed5c1bfcfc2c27e7ecf864e880f682792fd85) but rtd choked on that.
Right now, the solution is to have readthedocs build it editably as an explicitly invoked command, and similarly we ask developers to do this explicitly (`pip install -e ../.`) after they've built and moved into the environment.
Dan I'm not sure how the file addressing works inside rtd containers. As Carol Said they can be tricky