Fix small errors like unhandled exceptions etc.

gns3server/controller/node.py

@@ -175,7 +175,7 @@ class Node:
         if not os.path.isabs(path):
             path = os.path.join(self.project.controller.configs_path(), path)
         try:
-            with open(path) as f:
+            with open(path, encoding="utf-8") as f:
                 return f.read()
         except OSError:
             return None