failed to download af_za.json

Whenever I try to download Minecraft Snapshot 18w16a
it keeps saying: "Failed to download file. af_za.json"
it also says this:
Name: af_za.json
URL: http://resources.download.minecraft.net/71/71f90a6590b45bce954cae6a6bb06d32557f8156
Error details: UNKNOWN/-118
Filename on disk: 71f90a6590b45bce954cae6a6bb06d32557f8156
Path: C:/Users\Milton\AppData\Roaming\.minecraft\assets\objects\71/71f90a6590b45bce954cae6a6bb06d32557f8156
Exists: false