Mainly, as I spent a lot of time searching about these two errors, I thought it was a good idea to post here a short post with *all* error messages. Anyone searching for those would be kind of lucky to arrive here where the solution is written:
make a manual upgrade, no alternative.
Beside, it is a bit disappointing that the 'official' fix for a problem also leads to an error, moreover when this error *seems* to be just a missing file on your website (That's what we can read in the 'zip' file).
Anyway, I finally made a manual upgrade and despite the fact that it took much time (add the time searching for a comfortUpgrade fix

, it now runs 2.05+ without problem.