[tex-live] Problems installing TeX Live 2017 pre-test

[Akira Kakuto]

Dear Philip,

> I was then surprised to find that it wanted to run
> "mktexfmt xetex.fmt" and even more surprised to find
> that it failed ("Either -sys or -user mode is required").

I forgot to update "mktexfmt" command.
Please run fmtutil-sys before the use of TeX in order not to
execute the old mktexfmt at runtime.
I'll update the command after the release of TeX Live 2017.
For the other questions, I pass to Norbert.

Best,
Akira