i have following problem to intall python3-tk

master@cm /var/cache/apt/archives $ sudo apt-get install python3-tk
Reading package lists... Done
Building dependency tree       
Reading state information... Done
The following packages were automatically installed and are no longer required:
  libbonoboui2-0 libbonoboui2-common libgnomeui-0 libgnomeui-common
  python-gnome2
Use 'sudo apt autoremove' to remove them.
Suggested packages:
  tix python3-tk-dbg
The following NEW packages will be installed
  python3-tk
0 to upgrade, 1 to newly install, 0 to remove and 100 not to upgrade.
Need to get 25.1 kB of archives.
After this operation, 89.1 kB of additional disk space will be used.
Err:1 http://ftp.kfki.hu/linux/ubuntu xenial/main amd64 python3-tk amd64 3.5.1-1
  404  Not Found [IP: 148.6.0.24 80]
E: Failed to fetch http://ftp.kfki.hu/linux/ubuntu/pool/main/p/python3-stdlib-extensions/python3-tk_3.5.1-1_amd64.deb  404  Not Found [IP: 148.6.0.24 80]

E: Unable to fetch some archives, maybe run apt-get update or try with --fix-missing?