Attribution scanner error messages are unhelpful

In a recent failing integration, the attribution scanner reported:

    Could not parse file .../qtbase/src/testlib/3rdparty/catch2/qt_attribution.json: missing value separator
    Could not parse file .../qtbase/src/testlib/3rdparty/linux/qt_attribution.json: unterminated object

Notice, first, that the errors give no line numbers.

The "missing value separator" turned out to be that I'd used [...] around a Key: Value sequence that should have been enclosed in {...} – this took some noticing, as I was looking for a missing separator, which wasn't the actual problem.

The "unterminated object" turned out to be a missing comma after a new entry in a a Key: Value sequence. This really was a missing value separator, but wasn't reported as such.

In practice, these error messages were useless, beyond telling me which two files to examine, and actively distracting, by directing my attention to the wrong things.