Special case enum option parse failures.

[jsirois]

Display the valid choices to be more helpful. Also eliminate an unuseful
traceback from the option parse error message which always points to the
same internal option parsing code call stack.

Fixes #12277

[ci skip-rust]
[ci skip-build-wheels]

[jsirois]

Before:

$ ./pants dependencies --no-print-stacktrace --type=x src/python/pants/util/::
21:48:50.98 [ERROR] Error computing value for --type in scope 'dependencies' (may also be from PANTS_* environment variables).
Caused by:
ValueError: 'x' is not a valid DependencyType

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/home/jsirois/dev/pantsbuild/pants/src/python/pants/option/parser.py", line 582, in to_value_type
    return type_arg(val_str)
  File "/usr/lib/python3.7/enum.py", line 315, in __call__
    return cls.__new__(cls, value)
  File "/usr/lib/python3.7/enum.py", line 569, in __new__
    raise exc
  File "/usr/lib/python3.7/enum.py", line 553, in __new__
    result = cls._missing_(value)
  File "/usr/lib/python3.7/enum.py", line 582, in _missing_
    raise ValueError("%r is not a valid %s" % (value, cls.__name__))
ValueError: 'x' is not a valid DependencyType

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/home/jsirois/dev/pantsbuild/pants/src/python/pants/option/parser.py", line 284, in parse_args
    dest, kwargs, flag_vals, parse_args_request.passthrough_args
  File "/home/jsirois/dev/pantsbuild/pants/src/python/pants/option/parser.py", line 673, in _compute_value
    flag_vals = [to_value_type(expand(x)) for x in flag_val_strs]
  File "/home/jsirois/dev/pantsbuild/pants/src/python/pants/option/parser.py", line 673, in <listcomp>
    flag_vals = [to_value_type(expand(x)) for x in flag_val_strs]
  File "/home/jsirois/dev/pantsbuild/pants/src/python/pants/option/parser.py", line 617, in to_value_type
    return self.to_value_type(val_str, type_arg, member_type, dest)
  File "/home/jsirois/dev/pantsbuild/pants/src/python/pants/option/parser.py", line 585, in to_value_type
    f"Error applying type '{type_arg.__name__}' to option value '{val_str}', "
pants.option.errors.ParseError: Error applying type 'DependencyType' to option value 'x', for option '--type' in scope 'dependencies': 'x' is not a valid DependencyType


(Use --print-stacktrace for more error details and/or --no-process-execution-local-cleanup to inspect chroots and/or -ldebug for more logs. See https://www.pantsbuild.org/v2.6/docs/troubleshooting for common issues. Consider reaching out for help: https://www.pantsbuild.org/v2.6/docs/getting-help.)

After:

$ ./pants dependencies --no-print-stacktrace --type=x src/python/pants/util/::
21:48:29.31 [ERROR] Error computing value for --type in scope 'dependencies' (may also be from PANTS_* environment variables).
Caused by:
Invalid choice 'x'. Choose from: source, 3rdparty, source-and-3rdparty


(Use --print-stacktrace for more error details and/or --no-process-execution-local-cleanup to inspect chroots and/or -ldebug for more logs. See https://www.pantsbuild.org/v2.6/docs/troubleshooting for common issues. Consider reaching out for help: https://www.pantsbuild.org/v2.6/docs/getting-help.)

[benjyw]

Nice!

[Eric-Arellano]

Thanks, John!