Merge branch 'arity' into 'master'

Increase Boost Python function arity only when necessary

See merge request !36
2 jobs for master in 118 minutes (queued for 2 seconds)
Status Job ID Name Coverage
  Test
passed #4878
amd64
job_clang_amd64

01:58:00

passed #4877
amd64
job_gcc_amd64

01:36:35