As a workaround, I've changed the instruction to install the Chrome driver, to install the latest stable version. This should usually match up with the latest Chrome version, and if it does not, should eventually "catch up", whereas a hard-coded Chrome driver version will never "heal" once a new stable version of Chrome is released.
Travis CI builds currently fail as .travis.yml specifies that the latest stable Chrome is installed, but also that a Chrome driver only compatible with Chrome 74 is installed. Unfortunately, it does not seem that there is a way to specify exactly which Chrome version Travis CI installs.
As a workaround, I've changed the instruction to install the Chrome driver, to install the latest stable version. This should usually match up with the latest Chrome version, and if it does not, should eventually "catch up", whereas a hard-coded Chrome driver version will never "heal" once a new stable version of Chrome is released.