doc_open no longer hangs when LibreOffice has a question about the file
(a lock, a password, damage): it says what the problem is at once.
Fixed
doc_openhung for 60 s, then failed with a 504, when LibreOffice had a
question. It loaded with no interaction handler, so a file locked by
someone else (or by a crashed session), a password or a damaged file opened
a dialog nobody could answer. Every later call queued behind it. It now
answers at once:document_locked(with who holds the lock and since
when),password_requiredordocument_damaged, never retryable. Nelson
never removes a lock file and never approves anything on the user's
behalf. A CSV still opens: its import dialog takes the defaults
Added
doc_opentakesread_only, to read a document someone else has
locked without taking the lock