When trying to load the game, it gives the following message:

Failed to load mods: Error while loading item prototype "space-train-battery-pack" (item): ItemPrototype::fuel_category was removed. Please use ItemPrototype::fuel_categories.

The fix, in prototypes/items/items.lua (space-train-battery-pack item, ~line 33):

fuel_category = "electrical",

becomes:

fuel_categories = {"electrical"},

Note it must be the list form {"electrical"} — a dict-style {electrical = true} fails with "Value must be a list in property tree".

After editing the mod the mod loads fine on 2.1.20

The fix, in prototypes/items/items.lua (space-train-battery-pack item, ~line 33):

fuel_category = "electrical",

becomes:

fuel_categories = {"electrical"},

Note it must be the list form {"electrical"} — a dict-style {electrical = true} fails with "Value must be a list in property tree".

After editing the mod the mod loads fine on 2.1.20

That worked, thanks

Thank you so much dazzo31!

The latest version of PlanetsLib fixes this issue if you happen to play with a planet mod that requires it. Not a fix I'm happy to add, but it should make this issue less of a disturbance to players.