everytime i open the minecraft launcher and try update minecraft it comes up as system error. I've tried to fix it but nothing works. 

here are the details:

Name: netty-all-4.1.25.Final.jar
URL: https://libraries.minecraft.net/io/netty/netty-all/4.1.25.Final/netty-all-4.1.25.Final.jar
Error details: Request error -100: ERR_CONNECTION_CLOSED
Filename on disk: netty-all-4.1.25.Final.jar
Path: C:/Users\sthor180\AppData\Roaming\.minecraft\libraries\io/netty/netty-all/4.1.25.Final/netty-all-4.1.25.Final.jar
Exists: false

i hae no idea what this means