Multi file addons require their own folder.

The issue you are having is, addons is your addons folder.

Multifile addons require a folder of their own.

addons/
    my_addon/
        __init__.py
        foo.py

Instead you have placed all your files in the addons folder, hence it thinks panels.py is an addon to install, which is missing the bl_info dictionary.

Recently answered giving a run down on a multi file addon here Trying to make a menu using multiple modules

Multi file addons require their own folder.

The issue you are having is, addons is your addons folder. The error reports that all of your files are there. Having an __init__.py in your addons folder is a bad idea too. An init in a folder tells python to treat it as a module. Fortunately, I believe the devs foresaw this possibility and the folder is not directly import, otherwise you'd snaff up all the addons.

Instead if your addon is to be called my_addon and has another file foo.py create the structure like so

addons/
    my_addon/
        __init__.py
        foo.py

Having erroneously placed all files in the addons folder,it sees panels.py as an addon to install, which is missing the bl_info dictionary. -> The error.

Related

Recently answered giving a run down on a multi file addon here Trying to make a menu using multiple modules