Without this change, if the user does not have bash, `command` fails (as
it is a bash built-in). Explicitly set bash to be the shell.
Omit error messages of the `rm` command while cleaning.
- Be more obvious in `jupyter-repl-ret`
- Prefer shorter lines in `js/emacs-jupyter.js`
- Add `jupyter-repl-language`
- Refactor `jupyter-handle-error` for `jupyter-repl-client's
- Include margin width when fixing traceback spacing for python kernels
- Extract out special handling of python kernels in `jupyter-handle-error`
