Keno - take a look at what I did in https://github.com/ScottPJones/StringUtils.jl (building on the backs of giants, such as Tom Breloff, Dahua Lin, and others, incorporating some code from Formatting.jl). It solves problems I've had both with string literals, formatting, and outputting funny Unicode characters (without having to use UTF-8 in my source code).

I really like your Cxx.jl, that does seem to answer the issue raised here (are there any good features in pybind11 though that aren't already in Cxx.jl? that might be a good source for ideas on how to improve Cxx.jl if not)