I don't, from what Lex has said he originally made a dependency configuration that deobfed and added sources, then other people changed it to the current fg.deobf() tool and somehow the sources thing was lost, I'll look into how I might restore that
Two things here.
We do not support Magma or any other attempt to combine Forge and the Bukkit API.
We do not support 1.12.2 anymore because it's old and we've moved on.
You edited above the line.
So many people make this mistake, don't put your repositories inside the buildscript {} block, make your own repositories block below the stated line
You should always use the Forge version the pack is designed for.
It looks like the config is open in some other program while the game is trying to take complete control of it