anon@anon:~$ sudo apt-get update
Get:1 http://security.ubuntu.com/ubuntu bionic-security InRelease [88.7 kB]
Get:2 http://security.ubuntu.com/ubuntu bionic-security/main amd64 DEP-11 Metadata [204 B]
Hit:3 http://in.archive.ubuntu.com/ubuntu bionic InRelease
Get:4 http://security.ubuntu.com/ubuntu bionic-security/universe amd64 DEP-11 Metadata [20.8 kB]
Get:5 http://security.ubuntu.com/ubuntu bionic-security/universe DEP-11 48x48 Icons [12.2 kB]
Get:6 http://security.ubuntu.com/ubuntu bionic-security/universe DEP-11 64x64 Icons [45.2 kB]
Get:7 http://security.ubuntu.com/ubuntu bionic-security/multiverse amd64 DEP-11 Metadata [2,464 B]
Get:8 http://in.archive.ubuntu.com/ubuntu bionic-updates InRelease [88.7 kB]
Get:9 https://weechat.org/ubuntu bionic InRelease [3,999 B]
Err:9 https://weechat.org/ubuntu bionic InRelease
  The following signatures couldn't be verified because the public key is not available: NO_PUBKEY D1820DB22A11534E
Get:10 http://in.archive.ubuntu.com/ubuntu bionic-backports InRelease [74.6 kB]
Get:11 http://in.archive.ubuntu.com/ubuntu bionic-updates/main i386 Packages [450 kB]
Err:11 http://in.archive.ubuntu.com/ubuntu bionic-updates/main i386 Packages
  Hash Sum mismatch
  Hashes of expected file:
   - Filesize:449912 [weak]
   - SHA256:93ce1d95d1bc52381fb2d11594f51c7dec8f05c2aae246b02792330f6e0f38f4
   - SHA1:d08a3dba3f8cab4fbd00b84b1bb38666d5242e59 [weak]
   - MD5Sum:68cb5b5f300a30f34cb2f2fd58a40118 [weak]
  Hashes of received file:
   - SHA256:9ef8512c1fdf2d726a0fb111dede0add11905360eb1f0423f2307a87a5584e41
   - SHA1:9b282435ebecfd125eaf04854f9547407e8e6a97 [weak]
   - MD5Sum:bdc35b66ab6b9d7fe0697d3acd5ea1e6 [weak]
   - Filesize:449912 [weak]
  Last modification reported: Sat, 16 Feb 2019 00:46:51 +0000
  Release file created at: Sat, 16 Feb 2019 05:09:15 +0000
Get:12 http://in.archive.ubuntu.com/ubuntu bionic-updates/main amd64 Packages [523 kB]
Err:12 http://in.archive.ubuntu.com/ubuntu bionic-updates/main amd64 Packages

Get:13 http://in.archive.ubuntu.com/ubuntu bionic-updates/main Translation-en [195 kB]
Get:14 http://in.archive.ubuntu.com/ubuntu bionic-updates/main amd64 DEP-11 Metadata [278 kB]
Get:15 http://in.archive.ubuntu.com/ubuntu bionic-updates/main DEP-11 48x48 Icons [66.7 kB]
Get:16 http://in.archive.ubuntu.com/ubuntu bionic-updates/main DEP-11 64x64 Icons [123 kB]
Get:17 http://in.archive.ubuntu.com/ubuntu bionic-updates/restricted amd64 Packages [7,024 B]
Get:18 http://in.archive.ubuntu.com/ubuntu bionic-updates/restricted i386 Packages [6,988 B]
Get:19 http://in.archive.ubuntu.com/ubuntu bionic-updates/restricted Translation-en [3,076 B]
Get:20 http://in.archive.ubuntu.com/ubuntu bionic-updates/universe i386 Packages [721 kB]
Err:20 http://in.archive.ubuntu.com/ubuntu bionic-updates/universe i386 Packages

Get:21 http://in.archive.ubuntu.com/ubuntu bionic-updates/universe amd64 Packages [731 kB]
Err:21 http://in.archive.ubuntu.com/ubuntu bionic-updates/universe amd64 Packages

Get:22 http://in.archive.ubuntu.com/ubuntu bionic-backports/universe amd64 DEP-11 Metadata [7,352 B]
Reading package lists... Done
W: GPG error: https://weechat.org/ubuntu bionic InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY D1820DB22A11534E
E: The repository 'https://weechat.org/ubuntu bionic InRelease' is not signed.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.
anon@anon:~$ ^C