This trait was using private fields from its host classes
($this->event, $this->language). It created a weird coupling
situation where the host class uses the trait and the trait
uses the host class. Effectively a circular dependency.
Also, phan is complaining about it in
I65ae6adc10941c05a2646e551b1baa829e4e8654
Change-Id: Ib2796b7ca62ecd7ece19583d7ca83e4252a5d878
