Provide a different error message when socket does not exist

[NetSysFire]

Expected Behavior

You get an accurate error that the socket does not exist.

Current Behavior

You get a vague "key exchange failed" when /run/user/<uid>/org.keepassxc.KeePassXC.BrowserServer is not present due to e.g sandboxing via firejail which applies whitelisting.

Possible Solution

Better error message. I would have also edited the wiki to add that the socket location must be accessible but it is restricted. It has useful steps, but checking the socket location is missing.

This is not specific to my issue but ~/.mozilla/native-messaging-hosts should be accessible to the browser extension, so if org.keepassxc.keepassxc_browser.json does not exist you can provide a better error message here, too.

Steps to Reproduce (for bugs)

n/a

Debug info

KeePassXC - 2.7.1
KeePassXC-Browser - latest
Operating system: Linux
Browser: Firefox

[varjolintu]

The only good solution for this is to pass the error message from the browser directly to the popup, as an addition to "Key exchange failed".