[tests|analyser] know which files are parsed and which ones not

[cvandeplas]

use the parser function to list files and do a delta of the files present in the sysdiagnose.
Show which ones are covered and which ones are not yet parsed .
Ensure there's a way to exclude "known files with no value" to lower the amount of noise in the output.

Do this either as analyser (txt output) or unit test

[dario-br]

While it remains an analyser, some code maybe reused/re-think with the existing unit test: test/test_parsers.py

[dario-br]

The analyser output could also be simplified and just return the json, while leaving the html logic in a separate script.