ui: add explicit path to write prompt text bypassing buffers The prompt= flag was added at e35d7f131483, when colorui had its own write() function. Since we've merged colorui to ui, we can simply call the unbuffered write() function.

ui: write prompt text in ui.prompt(), not in ui._readline() self.label() is replaced by label= option, which should make it clearer why we can't pass the text to raw_input(prompt).