#328906 Show more user-friendly messages for network or unique index errors.

app/shared/constants.ts

@@ -15,5 +15,7 @@ export const imageWidth = 400;
 export const systemErrorMsgs = {
     'Iterator timed out': 'The operation took too long. Please try again later.',
     'Invalid request body': 'Something out of the ordinary happened. Please excuse us.',
-    'Invalid username or': 'Invalid e-mail or password.'
+    'Invalid username or': 'Invalid e-mail or password.',
+    'java.net.UnknownHostException': 'Could not reach server. Please check your internet connection',
+    'The operation results in a duplicate key': 'The name you chose is already taken. Please choose another one'
 };