I had problem doing sudo apt update for manually added repositories (I had problem with nodejs and docker) with my Ubuntu 17.10 VM running in VirtualBox. The error I get is Could not handshake: An unexpected TLS packet was received.
The following are steps that I took when trying to add docker repository and the output. The same thing happened when I tried to add nodejs as well.
sdnc-dev@sdncdev-VirtualBox:~/tools/idea-IC-173.4674.33/bin$ curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo apt-key add -
OK
sdnc-dev@sdncdev-VirtualBox:~/tools/idea-IC-173.4674.33/bin$ sudo apt-key fingerprint 0EBFCD88
pub   rsa4096 2017-02-22 [SCEA]
      9DC8 5822 9FC7 DD38 854A  E2D8 8D81 803C 0EBF CD88
uid           [ unknown] Docker Release (CE deb) <docker@docker.com>
sub   rsa4096 2017-02-22 [S]
sdnc-dev@sdncdev-VirtualBox:~/tools/idea-IC-173.4674.33/bin$ sudo add-apt-repository "deb [arch=amd64] https://download.docker.com/linux/ubuntu $(lsb_release -cs) stable"
[sudo] password for sdnc-dev: 
sdnc-dev@sdncdev-VirtualBox:~/tools/idea-IC-173.4674.33/bin$ sudo apt update 
Ign:1 https://download.docker.com/linux/ubuntu artful InRelease
Err:2 https://download.docker.com/linux/ubuntu artful Release
  Could not handshake: An unexpected TLS packet was received.
Hit:3 http://us.archive.ubuntu.com/ubuntu artful InRelease
Get:4 http://security.ubuntu.com/ubuntu artful-security InRelease [78.6 kB]
Get:5 http://us.archive.ubuntu.com/ubuntu artful-updates InRelease [78.6 kB]       
Get:6 http://us.archive.ubuntu.com/ubuntu artful-backports InRelease [72.2 kB]
Get:7 http://us.archive.ubuntu.com/ubuntu artful-updates/main amd64 Packages [226 kB]
Get:8 http://us.archive.ubuntu.com/ubuntu artful-updates/main i386 Packages [222 kB]
Get:9 http://us.archive.ubuntu.com/ubuntu artful-updates/main Translation-en [101 kB]
Get:10 http://us.archive.ubuntu.com/ubuntu artful-updates/universe i386 Packages [91.9 kB]
Get:11 http://us.archive.ubuntu.com/ubuntu artful-updates/universe amd64 Packages [92.8 kB]
Get:12 http://us.archive.ubuntu.com/ubuntu artful-updates/universe Translation-en [52.9 kB]
Reading package lists... Done              
E: The repository 'https://download.docker.com/linux/ubuntu artful Release' does not have a Release file.
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.
Here is the details of my setup:
   VM: Ubuntu 17.10
   VirtualBox 5.2.8 r121009 (Qt5.6.2)
   I am behind corporate proxy.
Does anyone know how to fix this?
 
     
     
    