Caqti forcing the use of Format which is thread unsafe

[craff]

Caqti is forcing us to use Logs which in turn uses Format. But,

• Format is slower than printf (around 70% slower)
• More importantly, Format is thread unsafe and, for instance, may raise the exception Queue.Empty (I got that bug) I reported this problem, but I am not sure Logs is thread safe.

Would be nice to be able to choose not to use Format.