feature request: python-prompt-toolkit integration, and my try at it

[vindarel]

Hi there,

some time ago I tried a bit at using the python prompt toolkit to enhance dg's repl experience. Indeed this projects makes it easy to have syntax highlighting, tooltip completions, history navigation and more.

I came up with https://gitlab.com/vindarel/ptdg (github mirror if you must), the basics work but it's unfinished, specially:

• it doesn't catch errors, so the repl fails
• it prints "None" after the results (that should be a minor stuff)

I think I didn't look how things are done in the dg repl soon enough, hence the limitations.

Just hoping this gives motivation to someone to do it. Even better would be a jupyter kernel, as referenced in another issue.