I notice that in addition to the complaints about nettle deprecation there is also a complaint about the use of memmove, unfortunately the compiler doesn't say what exactly it doesn't like about the use of memmove.
In raspbian I decided to go ahead and remove -Werror, a debdiff doing that should appear soon at https://debdiffs.raspbian.org/main/r/rdup . No intent to NMU in Debian.
