More informative error for non-existent package

[wholtz]

Checklist

• I added a descriptive title
• I searched open requests and couldn't find a duplicate

What is the idea?

Currently, if I try to lock the following:

name: base
platforms:
  - linux-64
channels:
  - conda-forge
dependencies:
  - not-a-real-package

the output is:

$ conda-lock lock -f bad-name.yaml
Locking dependencies for ['linux-64']...
INFO:conda_lock.conda_solver:linux-64 using specs ['not-a-real-package']
Traceback (most recent call last):
  File "/Users/willholtz/.local/bin/conda-lock", line 8, in <module>
    sys.exit(main())
             ^^^^^^
  File "/Users/willholtz/.local/pipx/venvs/conda-lock/lib/python3.11/site-packages/click/core.py", line 1157, in __call__
    return self.main(*args, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/willholtz/.local/pipx/venvs/conda-lock/lib/python3.11/site-packages/click/core.py", line 1078, in main
    rv = self.invoke(ctx)
         ^^^^^^^^^^^^^^^^
  File "/Users/willholtz/.local/pipx/venvs/conda-lock/lib/python3.11/site-packages/click/core.py", line 1688, in invoke
    return _process_result(sub_ctx.command.invoke(sub_ctx))
                           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/willholtz/.local/pipx/venvs/conda-lock/lib/python3.11/site-packages/click/core.py", line 1434, in invoke
    return ctx.invoke(self.callback, **ctx.params)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/willholtz/.local/pipx/venvs/conda-lock/lib/python3.11/site-packages/click/core.py", line 783, in invoke
    return __callback(*args, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/willholtz/.local/pipx/venvs/conda-lock/lib/python3.11/site-packages/click/decorators.py", line 33, in new_func
    return f(get_current_context(), *args, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/willholtz/.local/pipx/venvs/conda-lock/lib/python3.11/site-packages/conda_lock/conda_lock.py", line 1402, in lock
    lock_func(
  File "/Users/willholtz/.local/pipx/venvs/conda-lock/lib/python3.11/site-packages/conda_lock/conda_lock.py", line 1110, in run_lock
    make_lock_files(
  File "/Users/willholtz/.local/pipx/venvs/conda-lock/lib/python3.11/site-packages/conda_lock/conda_lock.py", line 393, in make_lock_files
    fresh_lock_content = create_lockfile_from_spec(
                         ^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/willholtz/.local/pipx/venvs/conda-lock/lib/python3.11/site-packages/conda_lock/conda_lock.py", line 836, in create_lockfile_from_spec
    deps = _solve_for_arch(
           ^^^^^^^^^^^^^^^^
  File "/Users/willholtz/.local/pipx/venvs/conda-lock/lib/python3.11/site-packages/conda_lock/conda_lock.py", line 748, in _solve_for_arch
    conda_deps = solve_conda(
                 ^^^^^^^^^^^^
  File "/Users/willholtz/.local/pipx/venvs/conda-lock/lib/python3.11/site-packages/conda_lock/conda_solver.py", line 160, in solve_conda
    dry_run_install = solve_specs_for_arch(
                      ^^^^^^^^^^^^^^^^^^^^^
  File "/Users/willholtz/.local/pipx/venvs/conda-lock/lib/python3.11/site-packages/conda_lock/conda_solver.py", line 396, in solve_specs_for_arch
    return _reconstruct_fetch_actions(conda, platform, dryrun_install)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/willholtz/.local/pipx/venvs/conda-lock/lib/python3.11/site-packages/conda_lock/conda_solver.py", line 252, in _reconstruct_fetch_actions
    if "LINK" not in dry_run_install["actions"]:
                     ~~~~~~~~~~~~~~~^^^^^^^^^^^
KeyError: 'actions'

That error wasn't very helpful. I dropped into the python debugger, and then I could see:

(Pdb) dry_run_install["error"]
"PackagesNotFoundError: The following packages are not available from current channels:\n\n  - not-a-real-package\n\nCurrent channels:\n\n  - https://conda.anaconda.org/conda-forge\n  - file:///var/folders/qq/q46r86t55t382q18lcxtk2tw0000gp/T/tmpqf06wj8e\n\nTo search for alternate channels that may provide the conda package you're\nlooking for, navigate to\n\n    https://anaconda.org\n\nand use the search bar at the top of the page.\n"

Why is this needed?

Make it easier to realize that you made a typo in a package name.

What should happen?

Display dry_run_install["error"] to the user.

Additional Context

No response