Attempt to fix chrome install on travis ci
Attempt to fix chrome install on travis ci

Currently failing with the following error:
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WARNING: The following packages cannot be authenticated!
  google-chrome-stable
E: There were unauthenticated packages and -y was used without --allow-unauthenticated
apt-get.diagnostics
apt-get install failed
The command "sudo -E apt-get -yq --no-install-suggests --no-install-recommends $(travis_apt_get_options) install google-chrome-stable" failed and exited with 100 during .
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Fix details documented here: https://docs.travis-ci.com/user/chrome

TradeMe/tractor,TradeMe/tractor,TradeMe/tractor