- Only check lower bound on conda/mamba, upgrade unbounded if not matched (let conda apply upper bound according to existing pins, such as Python)
- handle missing mamba
- avoid upgrading Python by aborting the install, instead of keeping old envs
- minimum supported Python for user env is 3.9
- Fix output reporting of conda install step (no need for json capture when we don't parse the output - exit codes will do)
miniconda downloader now provides sha256 hashes. Previously
it provided only md5 hashes. md5 is deprecated everywhere for
everything, so let's use this
We can no longer assume that sys.executable has conda
installed. Instead, we require that prefix has conda installed.
This requires miniconda to be installed into prefix.
