Travis is blocking Gradle apt source

[tswast]

From https://travis-ci.org/GoogleCloudPlatform/java-docs-samples/builds/166859196#L129

Adding APT Sources (BETA)
Disallowing sources: \{:sourceline\=\>"ppa:cwchien/gradle"\}
If you require these sources, please review the source approval process at: https://github.com/travis-ci/apt-source-whitelist#source-approval-process
$ export DEBIAN_FRONTEND=noninteractive
0.13s$ curl -sSL "https://ftp-master.debian.org/keys/archive-key-7.0.asc" | sudo -E apt-key add -
OK
0.01s$ echo "deb http://ftp.us.debian.org/debian unstable main contrib non-free" | sudo tee -a /etc/apt/sources.list > /dev/null
Installing APT Packages (BETA)
Disallowing packages: gradle-3.0
If you require these packages, please review the package approval process at: https://github.com/travis-ci/apt-package-whitelist#package-approval-process
$ export DEBIAN_FRONTEND=noninteractive
9.05s$ sudo -E apt-get -yq update &>> ~/apt-get-update.log
14.33s$ sudo -E apt-get -yq --no-install-suggests --no-install-recommends --force-yes install expect shellcheck

I'm not sure if we need this anymore or not. Maybe the Java Travis image comes with Gradle now?

[lesv]

try 3.1

[lesv]

Obsolete