Improve usability
Created originally on Bitbucket by paugier (Pierre Augier)
Was already merged in Bitbucket before import, marked as merged by the import user
- commandline option -pc -> -af (--accelerator-flags)
- Use autopep8 if black is not importable
- Raise error if error during Pythran/Cython compilation.
- Add warning when using a boosted module without compilation
- Add a warning: jit with unimportable accelerator