pinentry-gnome3 ncurses fallback blocked for a long time

pinentry-gnome3 should fall back to ncurses if it cannot contact the system prompter.

However, if D-Bus is available but a display is not (e.g. a ssh login with a user bus setup) an activated gcr-prompter will fail gtk_init and exit. The pinentry's gcr_system_prompt_open blocks until the BeginPrompting method call times out.

For this reason we can't have pinentry-gnome3 as a default pinentry implementation.

To reproduce without pinentry: python -c 'from gi.repository import Gcr; Gcr.SystemPrompt.open(0, None)'