First fix for #2325 (edit book table with readonly database)

cps/editbooks.py

@@ -1152,6 +1152,7 @@ def edit_list_book(param):
     vals = request.form.to_dict()
     book = calibre_db.get_book(vals['pk'])
     # ret = ""
+    try:
         if param == 'series_index':
             edit_book_series_index(vals['value'], book)
             ret = Response(json.dumps({'success': True, 'newValue': book.series_index}), mimetype='application/json')
@@ -1225,7 +1226,7 @@ def edit_list_book(param):
         else:
             return _("Parameter not found"), 400
         book.last_modified = datetime.utcnow()
-    try:
+
         calibre_db.session.commit()
         # revert change for sort if automatic fields link is deactivated
         if param == 'title' and vals.get('checkT') == "false":
@@ -1233,7 +1234,10 @@ def edit_list_book(param):
             calibre_db.session.commit()
     except (OperationalError, IntegrityError) as e:
         calibre_db.session.rollback()
-        log.error("Database error: %s", e)
+        log.error("Database error: {}".format(e))
+        ret = Response(json.dumps({'success': False,
+                                   'msg': 'Database error: {}'.format(e.orig)}),
+                       mimetype='application/json')
     return ret