bug#42920: conda 4.8.3 on guix cannot activate environments

[Ricardo Wurmus]

Hi Hugo,

> The conda 4.8.3 package on guix does not seem to work as expected.

Thanks for letting me know.  The upgrade took a long time and required
quite a bit of patching.

> But activating it does not work properly:
>
> hugo@alex ~$ conda activate testenv
>
> CommandNotFoundError: Your shell has not been properly configured to use
> 'conda activate'.
> To initialize your shell, run
>
>     $ conda init <SHELL_NAME>

This is very unfortunate, but perhaps we can work around this.
Initially I noticed that almost none of the Conda features worked
without “conda init”, so I decided to run “conda init” as part of the
build.  This installs a whole bunch of shell initialization files into
the prefix directory, which — I assume — are meant to be evaluated when
the shell starts.

So I suspect that you can get around this by manually sourcing the
appropriate shell init files.  Which of these need to be sourced
probably depends on your current shell.

> Unfortunately, conda init does not work well, because it needs root
> access: […]

Yeah, it’s a terrible design decision on the part of the Conda
developers.  Luckily you won’t need any of that because we already
installed all these files at build time.

> FWIW, maybe it would be simpler to create a micromamba package than a conda
> package:
> https://github.com/TheSnakePit/mamba

Why not both?

-- 
Ricardo