If I don't misread the docs, if a template is given, the file
is created in the current directory instead of the temporary
directory reported by QDir::tempPath()
Furthermore it cannot be set by env TMPDIR.
This issue drove me crazy (and no exceptions and no logs!)
until when I switched the server user to root (that is
of course not what we want).
As a temporary workaround, the server can be configured to
use /tmp or another www-data writeable directory as a working
directory.
By prefixing with tempPath() the file will be created
in the system temp directory.
