remove: dnf.yum.rpmtrans._WrapNoExceptions

It is silly and makes debugging harder. Most of all, RPM has long since been
fixed not to raise hell when a callback misbehaves [1].

[1] http://rpm.org/gitweb?p=rpm.git;a=commitdiff;h=09d43dcbdff4a450a72178d695db553c2f33ef27