Github user prabhjyotsingh commented on the issue:
https://github.com/apache/zeppelin/pull/2717
I had to use gecko because "Firefox is only fully supported at version
47.0.1 or earlier. Support
for later versions of firefox is provided by geckodriver"
Ref: https://github.com/SeleniumHQ/selenium/blob/master/java/CHANGELOG
Yes, I plan to upgrade version of Firefox as well, I was just waiting for
CI to pass as it used to pass on dist=precise (which uses FireFox 31)---
