Unbelievably, using a filename with spaces causes Lenovo XCC to return a message
with InternalError, 'The request failed due to an internal service error.
The service is still operational.'
As we're using a multipart update rather than a legacy HttpPushUriTargetsBusy
PATCHing, hardcoding should be quite safe.
It's actually quite hard to build a front-end for fwupd at the moment
as you're never sure when the progress bar is going to zip back to 0%
and start all over again. Some plugins go 0..100% for write, others
go 0..100% for erase, then again for write, then *again* for verify.
By creating a helper object we can easily split up the progress of the
specific task, e.g. write_firmware().
We can encode at the plugin level "the erase takes 50% of the time, the
write takes 40% and the read takes 10%". This means we can have a
progressbar which goes up just once at a consistent speed.
Only the backup BMC device (which we ignore anyway...) can be updated
by specifying the target ID, the others need an *empty* array so that
XCC can work out what devices need to be processed.
