bug#39491: 28.0.50; two bugs in battery-upower

[Eli Zaretskii]

> From: Richard Stallman <rms@gnu.org>
> Date: Fri, 07 Feb 2020 15:14:57 -0500
> 
> 
> battery-upower crashes on my laptop because there is no BatteryLevel property.
> This code
> 
>           (cons ?b (cond ((= level 3) "-")
>                          ((= level 4) "!")
>                          (online-p "+")
>                          (t "")))
> 
> needs to handle nil.  I don't know what value it should return for that case.
> 
> However, that function has a design flaw: it reports on just the first
> battery in the list.  battery-upower-device-list correctly returns a
> list with an element for each battery, but battery-upower finds only one
> of them (the first one in the list) and ignores the others.
> 
> The old code handle all the batteries and added the energy quantities
> so as to report accurately the total power available and overall
> fraction of charge.  I wrote that code myself, around 10 years ago.
> 
> Please restore the lost functionality.

Evgeny, could you please look into fixing this?

TIA