Probably missing copy of body to plain in carbon and privmessage.
Only covers the incoming message path because goal is OMEMO decryption
of untrusted message.
Cover some of the log functions but not all.
This handler redirects stderr output to a pipe and gathers logs from the
read end.
The handler is called from main loop, therefore, if a function prints logs
to stderr they will be put to log file only after function returns.