runtime: APT repo returns gnutls_handshake() failed: Handshake failed

Steps to reproduce

Try to install .NET Core on Ubuntu 14.04 by following steps on https://www.microsoft.com/net/core#linuxubuntu

Expected behavior

It works.

Actual behavior

It fails to fetch the packages from the repo, which means .NET Core can’t be installed:

W: Failed to fetch https://apt-mo.trafficmanager.net/repos/dotnet-release/dists/trusty/main/binary-amd64/Packages  gnutls_handshake() failed: Handshake failed

E: Some index files failed to download. They have been ignored, or old ones used instead.

Interestingly, fetching the file via curl/wget succeeds. But gnutls-cli prints this:

$ gnutls-cli -p 443 apt-mo.trafficmanager.net
Resolving 'apt-mo.trafficmanager.net'...
Connecting to '13.80.10.205:443'...
*** Fatal error: A TLS fatal alert has been received.
*** Received alert [40]: Handshake failed
*** Handshake has failed
GnuTLS error: A TLS fatal alert has been received.

This breaks all .NET Core builds on Travis: https://github.com/travis-ci/travis-ci/issues/7565

It seems to have started yesterday/today as I have a successful build from 16 hours ago.

Environment data

Ubuntu 14.04