detecting if wget and pip are installed on MacOS

[gfursin]

Hi @ens-lg4 .

It will be nice to brainstorm how to automatically detect wget and pip on MacOS (or maybe even on other systems too) when required for some packages, and either report users that they need to install these dependencies, or even maybe install them automatically.

We can also detect if pip is old (i.e. if it gives an issue with user/global installation flag) and suggest to upgrade it or do it automatically ... These are very common issues which I saw at SC18 ...

Thanks!