Improve Error-Messages

Hi guys,

thx for your tool! Your concept is really cool and a handy feature :)

I have decided to integrate this tool in my Snakemake-Pipeline.
However, I now already stumbled multiple times over the issue of having metadata-files that fail the eido evaluation, but the Error messages which are returned by the tool are not helping at all.
Thus, every time when I face such an error I have to invest a lot of time to finally figure out what's the reason for the failing validation.

Here is a minimal reproducible example:

1. pep_schemal.yaml

description: Minimal example

imports:
   - http://schema.databio.org/pep/2.1.0.yaml

properties:
  samples:
    type: array
    items:
      type: object
      properties:
        sample_directory:
          type: string
          pattern: "^/\\S+$|None"

2. input_no_error.csv

sample_name,sample_directory
test,/testung

3. input_error.csv

sample_name,sample_directory
test,testung

Then the output:

# No error
$ eido validate input_no_error.csv -s pep_schema.yaml
Validation successful

# Error
$ eido validate input_error.csv -s pep_schema.yaml
Traceback (most recent call last):
  File "/Users/oliverkuchler/miniforge3/envs/snakemake7/bin/eido", line 10, in <module>
    sys.exit(main())
             ^^^^^^
  File "/Users/oliverkuchler/miniforge3/envs/snakemake7/lib/python3.12/site-packages/eido/cli.py", line 159, in main
    validator(*arguments)
  File "/Users/oliverkuchler/miniforge3/envs/snakemake7/lib/python3.12/site-packages/eido/validation.py", line 73, in validate_project
    _validate_object(
  File "/Users/oliverkuchler/miniforge3/envs/snakemake7/lib/python3.12/site-packages/eido/validation.py", line 45, in _validate_object
    instance_name = error.instance[sample_name_colname]
                    ~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^

Is there any plans for the future to improve the output?
It would be very cool if one could at least see, because of which input the validation fails.

Start with eido/validation.py around _validate_object and the traceback path from eido/cli.py. Reproduce the failure with input_error.csv and pep_schema.yaml, then inspect how validation errors are surfaced. Done means the invalid input reports a useful validation reason and context instead of an unhelpful traceback.