There are two warnings when running manual tests:
[ThemeImporter] Failed to find "/workspace/ckeditor5/packages/ckeditor5-theme-lark/theme/ckeditor5-table/table.css".
[ThemeImporter] Failed to find "/workspace/ckeditor5/packages/ckeditor5-theme-lark/theme/ckeditor5-table/inserttable.css".
Hm... actually, there are more warnings when running --files=core (previously I was testing --files=mention):

What could have changed? Or were there always there? If they were... they are confusing and we should get rid of them.
cc @oleq
They were always there. They happen if a feature CSS file ckeditor5-foo/theme/bar.css has no counterpart in ckeditor5-theme-lark/theme/ckeditor5-foo/bar.css.
At first, it helped to figure out obvious bugs (_I wrote my theme styles but they don't work..._ (a.k.a. _I made a typo..._)) but now I suppose with more and more packages, I agree this might actually be annoying.
I'm OK with removing them completely.
I was inspecting the dev environment and I can see two ways of dealing with this:
debug: true from theme importer options for manual testsverbose option there to include missing files warningsI'd go with 1:

I don't know why we need all the Loading for "foo/bar.css" logs are there anyway and I never read them.
Option 2: If you wish we might leave the debug: true there (so some noise will still be there) but no warning will be outputted.
Option 3: Similar to option 2 but no-one will ever know if some missing counterpart file type of warning.
I don't know why we need all the
Loading for "foo/bar.css"logs are there anyway and I never read them.
That's a good point I guess. Only errors should land here.
Most helpful comment
They were always there. They happen if a feature CSS file
ckeditor5-foo/theme/bar.csshas no counterpart inckeditor5-theme-lark/theme/ckeditor5-foo/bar.css.At first, it helped to figure out obvious bugs (_I wrote my theme styles but they don't work..._ (a.k.a. _I made a typo..._)) but now I suppose with more and more packages, I agree this might actually be annoying.
I'm OK with removing them completely.