Specifying multiple python versions on conda build results in an error

[mikev-junimo]

Checklist

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• I searched open reports and couldn't find a duplicate

What happened?

When I run conda-build 3.27.0 with multiple python versions, e.g., conda build --py 3.10 --py 3.11 I get the following exception:

# >>>>>>>>>>>>>>>>>>>>>> ERROR REPORT <<<<<<<<<<<<<<<<<<<<<<

    Traceback (most recent call last):
      File "/spare/local/devtools/conda-env/lib/python3.11/site-packages/conda/exception_handler.py", line 17, in __call__
        return func(*args, **kwargs)
               ^^^^^^^^^^^^^^^^^^^^^
      File "/spare/local/devtools/conda-env/lib/python3.11/site-packages/conda/cli/main.py", line 78, in main_subshell
        exit_code = do_call(args, parser)
                    ^^^^^^^^^^^^^^^^^^^^^
      File "/spare/local/devtools/conda-env/lib/python3.11/site-packages/conda/cli/conda_argparse.py", line 142, in do_call
        result = plugin_subcommand.action(getattr(args, "_args", args))
                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
      File "/spare/local/devtools/conda-env/lib/python3.11/site-packages/conda_build/plugin.py", line 10, in build
        execute(*args, **kwargs)
      File "/spare/local/devtools/conda-env/lib/python3.11/site-packages/conda_build/cli/main_build.py", line 568, in execute
        outputs = api.build(
                  ^^^^^^^^^^
      File "/spare/local/devtools/conda-env/lib/python3.11/site-packages/conda_build/api.py", line 253, in build
        return build_tree(
               ^^^^^^^^^^^
      File "/spare/local/devtools/conda-env/lib/python3.11/site-packages/conda_build/build.py", line 3777, in build_tree
        metadata_tuples = render_recipe(
                          ^^^^^^^^^^^^^^
      File "/spare/local/devtools/conda-env/lib/python3.11/site-packages/conda_build/render.py", line 969, in render_recipe
        m = MetaData(recipe_dir, config=config)
            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
      File "/spare/local/devtools/conda-env/lib/python3.11/site-packages/conda_build/metadata.py", line 1111, in __init__
        self.parse_again(permit_undefined_jinja=True, allow_no_other_outputs=True)
      File "/spare/local/devtools/conda-env/lib/python3.11/site-packages/conda_build/metadata.py", line 1203, in parse_again
        self._get_contents(
      File "/spare/local/devtools/conda-env/lib/python3.11/site-packages/conda_build/metadata.py", line 1880, in _get_contents
        env.globals.update(get_selectors(self.config))
                           ^^^^^^^^^^^^^^^^^^^^^^^^^^
      File "/spare/local/devtools/conda-env/lib/python3.11/site-packages/conda_build/metadata.py", line 143, in get_selectors
        defaults = variants.get_default_variant(config)
                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
      File "/spare/local/devtools/conda-env/lib/python3.11/site-packages/conda_build/variants.py", line 123, in get_default_variant
        base.update(_get_default_compilers(config.platform, python))
                    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    TypeError: unhashable type: 'list'

Conda Info

No response

Conda Config

No response

Conda list

No response

Additional Context

No response

[github-actions]

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