Description of your issue:

Getting the following during shippable build failed:
The following signatures couldn't be verified because the public key is not available: NO_PUBKEY E91335D77E3E87CB Ign:31 https://packagecloud.io/basho/riak/ubuntu xenial/main Sources Get:48 https://packagecloud.io/github/git-lfs/ubuntu xenial/main amd64 Packages [9,119 B] Ign:37 https://packagecloud.io/basho/riak/ubuntu xenial/main amd64 Packages Ign:35 https://packagecloud.io/basho/riak/ubuntu xenial/main all Packages Err:31 https://packagecloud.io/basho/riak/ubuntu xenial/main Sources 402 Payment Required Ign:37 https://packagecloud.io/basho/riak/ubuntu xenial/main amd64 Packages Ign:35 https://packagecloud.io/basho/riak/ubuntu xenial/main all Packages Fetched 7,922 kB in 3s (2,565 kB/s) Reading package lists... W: An error occurred during the signature verification. The repository is not updated and the previous index files will be used. GPG error: http://dl.yarnpkg.com/debian stable InRelease: The following signatures were invalid: KEYEXPIRED 1507181400 KEYEXPIRED 1546376218 KEYEXPIRED 1546372003 KEYEXPIRED 1580619281 KEYEXPIRED 1580607983 KEYEXPIRED 1580619281 KEYEXPIRED 1507181400 KEYEXPIRED 1546376218 KEYEXPIRED 1546372003 KEYEXPIRED 1580619281 KEYEXPIRED 1580607983 KEYEXPIRED 1507181400 KEYEXPIRED 1546376218 KEYEXPIRED 1546372003 KEYEXPIRED 1580619281 KEYEXPIRED 1580607983 W: The repository 'https://packagecloud.io/basho/riak/ubuntu xenial Release' does not have a Release file. W: An error occurred during the signature verification. The repository is not updated and the previous index files will be used. GPG error: https://downloads.apache.org/cassandra/debian 311x InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY E91335D77E3E87CB W: Failed to fetch http://www.apache.org/dist/cassandra/debian/dists/311x/InRelease The following signatures couldn't be verified because the public key is not available: NO_PUBKEY E91335D77E3E87CB W: Failed to fetch http://dl.yarnpkg.com/debian/dists/stable/InRelease The following signatures were invalid: KEYEXPIRED 1507181400 KEYEXPIRED 1546376218 KEYEXPIRED 1546372003 KEYEXPIRED 1580619281 KEYEXPIRED 1580607983 KEYEXPIRED 1580619281 KEYEXPIRED 1507181400 KEYEXPIRED 1546376218 KEYEXPIRED 1546372003 KEYEXPIRED 1580619281 KEYEXPIRED 1580607983 KEYEXPIRED 1507181400 KEYEXPIRED 1546376218 KEYEXPIRED 1546372003 KEYEXPIRED 1580619281 KEYEXPIRED 1580607983 E: Failed to fetch https://packagecloud.io/basho/riak/ubuntu/dists/xenial/main/source/Sources 402 Payment Required W: Some index files failed to download. They have been ignored, or old ones used instead.
NOTE: If you are experiencing a build failure, please include:

• https://app.shippable.com/github/1eq/1EQ/runs/10792/1/console

My Yml configuration

- sudo update-alternatives --set php /usr/bin/php7.1
- php7.1 -v
- python ./build/notify.py --slack-url $SLACK_URL --message started
- curl -sS https://getcomposer.org/installer | sudo php7.1 -- --install-dir=/usr/local/bin --filename=composer
- php7.1 /usr/local/bin/composer self-update
- cp app/config/config_template.php app/config/config.php
- mkdir -p shippable/codecoverage
- mkdir -p shippable/testresults
#- apt-key list
#- sudo apt-key adv --keyserver pool.sks-keyservers.net --refresh-keys
- sudo apt-get update
- sudo apt-key adv --keyserver pool.sks-keyservers.net --recv-key E91335D77E3E87CB
- sudo apt-get install python-software-properties
- sudo apt-add-repository -y ppa:brightbox/ruby-ng
- curl -sS https://dl.yarnpkg.com/debian/pubkey.gpg | sudo apt-key add
- sudo apt-get update