Improve copy_csv's error when the file does not exists.

[PimMeulensteen]

(lr_module_scratch-3.13) pimmeulensteen@pims-laptop ~/D/P/lr_module_scratch (main) [1]> time pdm run lir lrmodule/models/firing_pin_impression/validation.yaml
Traceback (most recent call last):
  File "/Users/pimmeulensteen/Documents/Projects/lr_module_scratch/.venv/lib/python3.13/site-packages/lir/experiments/base_experiment.py", line 152, in run
    self._generate_and_run()
    ~~~~~~~~~~~~~~~~~~~~~~^^
  File "/Users/pimmeulensteen/Documents/Projects/lr_module_scratch/.venv/lib/python3.13/site-packages/lir/experiments/predefined_experiment.py", line 55, in _generate_and_run
    split_data = list(splitter.apply(provider.get_instances()))
                                     ~~~~~~~~~~~~~~~~~~~~~~^^
  File "/Users/pimmeulensteen/Documents/Projects/lr_module_scratch/.venv/lib/python3.13/site-packages/lir/datasets/feature_data_csv.py", line 278, in get_instances
    with open(path) as f:
         ~~~~^^^^^^
FileNotFoundError: [Errno 2] No such file or directory: '/Users/pimmeulensteen/Documents/Projects/lr_module_scratch/data/firing_pin_impression2.csv'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/Users/pimmeulensteen/Documents/Projects/lr_module_scratch/.venv/bin/lir", line 8, in <module>
    sys.exit(main())
             ~~~~^^
  File "/Users/pimmeulensteen/Documents/Projects/lr_module_scratch/.venv/lib/python3.13/site-packages/lir/main.py", line 233, in main
    experiment.run()
    ~~~~~~~~~~~~~~^^
  File "/Users/pimmeulensteen/Documents/Projects/lr_module_scratch/.venv/lib/python3.13/site-packages/lir/experiments/base_experiment.py", line 155, in run
    output.close()
    ~~~~~~~~~~~~^^
  File "/Users/pimmeulensteen/Documents/Projects/lr_module_scratch/lrmodule/copy_csv.py", line 49, in close
    df = pd.read_csv(self.source_file)
  File "/Users/pimmeulensteen/Documents/Projects/lr_module_scratch/.venv/lib/python3.13/site-packages/pandas/io/parsers/readers.py", line 1026, in read_csv
    return _read(filepath_or_buffer, kwds)
  File "/Users/pimmeulensteen/Documents/Projects/lr_module_scratch/.venv/lib/python3.13/site-packages/pandas/io/parsers/readers.py", line 620, in _read
    parser = TextFileReader(filepath_or_buffer, **kwds)
  File "/Users/pimmeulensteen/Documents/Projects/lr_module_scratch/.venv/lib/python3.13/site-packages/pandas/io/parsers/readers.py", line 1620, in __init__
    self._engine = self._make_engine(f, self.engine)
                   ~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^
  File "/Users/pimmeulensteen/Documents/Projects/lr_module_scratch/.venv/lib/python3.13/site-packages/pandas/io/parsers/readers.py", line 1880, in _make_engine
    self.handles = get_handle(
                   ~~~~~~~~~~^
        f,
        ^^
    ...<6 lines>...
        storage_options=self.options.get("storage_options", None),
        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    )
    ^
  File "/Users/pimmeulensteen/Documents/Projects/lr_module_scratch/.venv/lib/python3.13/site-packages/pandas/io/common.py", line 873, in get_handle
    handle = open(
        handle,
    ...<3 lines>...
        newline="",
    )
FileNotFoundError: [Errno 2] No such file or directory: '/Users/pimmeulensteen/Documents/Projects/lr_module_scratch/data/firing_pin_impression2.csv'

This current state is quite verbose, but not very clear. Using something like:

if not self.source_file.is_file():
    raise FileNotFoundError(f"CopyCSV: File to copy '{self.source_file}' does not exist.")

would result in something like this

(lr_module_scratch-3.13) pimmeulensteen@pims-laptop ~/D/P/lr_module_scratch (main) [1]> time pdm run lir lrmodule/models/firing_pin_impression/validation.yaml
Traceback (most recent call last):
  File "/Users/pimmeulensteen/Documents/Projects/lr_module_scratch/.venv/bin/lir", line 8, in <module>
    sys.exit(main())
             ~~~~^^
  File "/Users/pimmeulensteen/Documents/Projects/lr_module_scratch/.venv/lib/python3.13/site-packages/lir/main.py", line 204, in main
    experiments, output_dir = initialize_experiments(confidence.loadf(args.setup))
                              ~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/pimmeulensteen/Documents/Projects/lr_module_scratch/.venv/lib/python3.13/site-packages/lir/main.py", line 104, in initialize_experiments
    return parse_experiments(cfg, output_dir), output_dir
           ~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^
  File "/Users/pimmeulensteen/Documents/Projects/lr_module_scratch/.venv/lib/python3.13/site-packages/lir/config/experiment_strategies.py", line 343, in parse_experiments
    experiment = parse_experiment_strategy(
        exp_config,
        output_path,
    )
  File "/Users/pimmeulensteen/Documents/Projects/lr_module_scratch/.venv/lib/python3.13/site-packages/lir/config/experiment_strategies.py", line 320, in parse_experiment_strategy
    return strategy_parser.parse(config, output_path)
           ~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^
  File "/Users/pimmeulensteen/Documents/Projects/lr_module_scratch/.venv/lib/python3.13/site-packages/lir/config/experiment_strategies.py", line 171, in parse
    exp = self.get_experiment(experiment_name)
  File "/Users/pimmeulensteen/Documents/Projects/lr_module_scratch/.venv/lib/python3.13/site-packages/lir/config/experiment_strategies.py", line 197, in get_experiment
    self.output_list(),
    ~~~~~~~~~~~~~~~~^^
  File "/Users/pimmeulensteen/Documents/Projects/lr_module_scratch/.venv/lib/python3.13/site-packages/lir/config/experiment_strategies.py", line 69, in output_list
    return parse_aggregations(config, self._output_dir)
  File "/Users/pimmeulensteen/Documents/Projects/lr_module_scratch/.venv/lib/python3.13/site-packages/lir/config/aggregation.py", line 87, in parse_aggregations
    return [parse_aggregation(item, output_dir, context) for i, item in enumerate(config)]
            ~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/pimmeulensteen/Documents/Projects/lr_module_scratch/.venv/lib/python3.13/site-packages/lir/config/aggregation.py", line 54, in parse_aggregation
    parsed_object = parser.parse(config, output_dir)
  File "/Users/pimmeulensteen/Documents/Projects/lr_module_scratch/.venv/lib/python3.13/site-packages/lir/config/base.py", line 368, in parse
    return func(config, output_dir)  # type: ignore
  File "/Users/pimmeulensteen/Documents/Projects/lr_module_scratch/lrmodule/copy_csv.py", line 61, in copy_csv
    return CopyCSV(source_file, output_dir, columns=columns, new_file_name=new_file_name)
  File "/Users/pimmeulensteen/Documents/Projects/lr_module_scratch/lrmodule/copy_csv.py", line 26, in __init__
    raise FileNotFoundError(f"CopyCSV: File to copy '{self.source_file}' does not exist.")
FileNotFoundError: CopyCSV: File to copy '/Users/pimmeulensteen/Documents/Projects/lr_module_scratch/data/firing_pin_impression2.csv' does not exist.

which is - in my opinion - more clear.