Previously we would fail with a generic message suggesting to run gargantext-init, but that wouldn't always be the case; sometimes there might be problems connecting to the database, and we want to show the raw exception. This code should help diagnosing what's wrong.

It also changes the error hint to report the correct executable, as these days we use gargantext-cli init instead.

Specifically, I had setup my Linux version of Gargantext to use my Mac's DB (so that I wouldn't lose previous data), but with the current code on dev we would get a misleading suggestion of running gargantext-cli init, whereas the real problem was that I couldn't even connect to the DB. This MR fixes that by showing what's really wrong.