argument --experimental-solver: invalid choice: 'libmamba' (choose from 'classic')

[pvanheus]

Describe the bug
In a newly installed Galaxy, running from run.sh, when the system tries to install packages using conda the following error happens:

galaxy.tool_util.deps.conda_util DEBUG 2023-05-21 12:48:01,580 [pN:main.1,p:381422,tN:WSGI_9] Executing command: /home/pvh/Documents/code/SANBI/projects/galaxy/galaxy/database/dependencies/_conda/bin/conda create -y --quiet --experimental-solver libmamba --override-channels --channel conda-forge --channel bioconda --channel defaults --name __gzip@_uv_ gzip
uvicorn.access INFO 2023-05-21 12:48:01,884 [pN:main.1,p:381422,tN:MainThread] 127.0.0.1:59296 - "GET /api/tool_shed_repositories?name=mosdepth&owner=iuc HTTP/1.1" 200
usage: conda create [-h] [--clone ENV] (-n ENVIRONMENT | -p PATH) [-c CHANNEL]
                    [--use-local] [--override-channels]
                    [--repodata-fn REPODATA_FNS] [--experimental {jlap,lock}]
                    [--strict-channel-priority] [--no-channel-priority]
                    [--no-deps | --only-deps] [--no-pin] [--copy] [-C] [-k]
                    [--offline] [-d] [--json] [-q] [-v] [-y] [--download-only]
                    [--show-channel-urls] [--file FILE]
                    [--no-default-packages]
                    [--solver {classic} | --experimental-solver {classic}]
                    [--dev]
                    [package_spec ...]
conda create: error: argument --experimental-solver: invalid choice: 'libmamba' (choose from 'classic')

Galaxy was installed in a WSL2-hosted Ubuntu 22.04 environment where conda was already present. The existing conda is conda-version 23.3.1 installed from mambaforge.

Galaxy Version and/or server at which you observed the bug
Galaxy Version: 23.1
Commit: ec017ff

To Reproduce
Steps to reproduce the behavior:

1. Clone Galaxy source code.
2. In an existing conda base environment (details above) run the run.sh in the Galaxy source directory
3. Create an admin account and try and install a tool
4. The error described is shown in the logs.

Expected behavior
The libmamba solver is not automatically available in conda. If it is not present, Galaxy needs to install it (conda install -n base conda-libmamba-solver) or notify the admin to do so. In fact, activating the conda that Galaxy installs in database/dependencies/_conda and running this command solves this problem.

[bernt-matthias]

Interesting. Is this a setup using containers (if so, are you using a build resolver?) or conda?

We may switch to mamba anyway.. xref #15984

[pvanheus]

Interesting. Is this a setup using containers (if so, are you using a build resolver?) or conda?

We may switch to mamba anyway.. xref #15984

This setup was not using containers - it was the "out of the box" Galaxy from Github with no config options set besides the admin_user.

[tuncK]

I was describing the same problem to @nsoranzo ~2 months ago. Literally happens out of the box, directly on linux VM or laptop, and it does not help clearing any reasonable caches or updating pip/conda etc.