Hi,
Thanks for your message. This is nothing to worry about. SalvusFlow is an optional submodule for running jobs on remote clusters, which is currently still in an experimental phase. SalvusFlow is not needed to create meshes or to run simulations on the same computer on which you are installing Salvus.
You should be able to continue with `make -j` to install SalvusWave and SalvusMesher together with some other dependencies.
If you still want to install SalvusFlow you can add the missing python packages with conda. Usually this requires
`conda install celery paramiko flask tqdm arrow redis redis-py networkx click`
Cheers
Christian