snakemake: archive just conda envs as yaml

After each snakemake pipeline run, I'd like to save a yaml export of each conda env (via onsuccess:). One can create a tarball of the entire pipeline, but I just want to export the conda envs as yaml files, especially given how long it can take to create a tarball of everything. I have not found a good way of doing this, especially in regards to associating the conda env name in the workflow with the md5 used in .snakemake/conda/.