If I read the code
buildbot.data.logs.Log.newLog: adds an increment to the slug until 50 same slug exist.
I'd remove that check for the same name. (More than 50 will happen scarcely).

Regarding the sanity check of the slug, there does not seem to be any.
Anyway, I'll remove all those check and let the other methods like ascii2unicode, which translates the name
to the first slug, handle that issue.