fluentd logs: no implicit conversion of nil into String

Issue

After setting up OpenShift Aggregate Logging, the fluentd logs contain:

2016-06-14 06:48:52 -0400 [info]: reading config file path="/etc/fluent/fluent.conf"
2016-06-14 06:49:00 -0400 [warn]: failed to expand `%Q[#{ Time.at(time) > Time.now ? (temp_time = Time.parse(Time.at(time).to_s.gsub(Time.at(time).year.to_s, (tag_parts[3].nil? ? Time.at(time).year.to_s : tag_parts[3][9,4]) )).to_datetime.to_s; Time.parse(temp_time) > Time.now ? Time.parse(temp_time.gsub(Time.parse(temp_time).year.to_s, (Time.parse(temp_time).year - 1).to_s )).to_datetime.to_s : Time.parse(temp_time).to_datetime.to_s ) : Time.at(time).to_datetime.to_s }]` error_class=TypeError error="no implicit conversion of nil into String"