clearer error and suggestion when c-analyzer cannot read ignored.tsv

[iritkatriel]

    for data, failure in check(analysis):
                         ^^^^^^^^^^^^^^^
  File "/home/runner/work/cpython/cpython/Tools/c-analyzer/cpython/_analyzer.py", line 425, in check_globals
    ignored = read_ignored()
              ^^^^^^^^^^^^^^
  File "/home/runner/work/cpython/cpython/Tools/c-analyzer/cpython/_analyzer.py", line 123, in read_ignored
    _IGNORED.update(_datafiles.read_ignored(IGNORED_FILE, relroot=REPO_ROOT))
                    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/runner/work/cpython/cpython/Tools/c-analyzer/c_analyzer/datafiles.py", line 93, in read_ignored
    return dict(_iter_ignored(infile, relroot))
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/runner/work/cpython/cpython/Tools/c-analyzer/c_analyzer/datafiles.py", line 112, in _iter_ignored
    raise e
  File "/home/runner/work/cpython/cpython/Tools/c-analyzer/c_analyzer/datafiles.py", line 108, in _iter_ignored
    varid = _info.DeclID.from_row(varidinfo)
            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/runner/work/cpython/cpython/Tools/c-analyzer/c_parser/info.py", line 207, in from_row
    return cls(*row)
           ^^^^^^^^^
TypeError: DeclID.__new__() missing 3 required positional arguments: 'filename', 'funcname', and 'name'
Error occured when processing the row [] in /home/runner/work/cpython/cpython/Tools/c-analyzer/cpython/ignored.tsv.
Could it be that you added a row which is not tab-delimited?

The PR adds the last two lines to the error.

[StanFromIreland]

Looks good to me. Very nice addition for users too.