VMM/mailbox: Decode error messages from doveadm. Those errors occur only with the dbox mailbox format when the mailbox.folders contains non-ASCII mailbox names.

# use glob syntax.
syntax: glob

*~
*.py?
.*.swp
.swp
build
debian/vmm
debian/*.log
debian/*.debhelper
debian/files
debian/*substvars
.pc
*.egg-info