21.3 is not installed. Downloading and installing pre-build binary.
Downloading archive: https://storage.googleapis.com/travis-ci-language-archives/erlang/binaries/ubuntu/18.04/x86_64/erlang-21.3-nonroot.tar.bz2
0.05s$ wget -o ${TRAVIS_HOME}/erlang.tar.bz2 ${archive_url}
The command "wget -o ${TRAVIS_HOME}/erlang.tar.bz2 ${archive_url}" failed and exited with 8 during .
Your build has been stopped.
Though wget -o <.tar.bz2> is weird: it redirects output messages to the file. The programmer probably meant -O (this is different from curl so easy to mix up).