Selenium deprecated a lof of errors to comply with W3C specification starting from version 3.141.592

Current test runs on selenium-webdriver 3.141.592 and up, produce a lof of deprecation warnings from selenium:
2019-04-22 08:40:17 WARN Selenium [DEPRECATION] Selenium::WebDriver::Error::UnhandledError is deprecated. Use Selenium::WebDriver::Error::UnknownError (ensure the driver supports W3C WebDriver specification) instead.

#276 should fix it