branch-1 docker mode for yetus fails

15:30:41  Step 28/33 : RUN gem install rubocop:'<= 0.81'
15:30:41   ---> Running in 21103fb7944c
15:30:42  Building native extensions.  This could take a while...
15:30:43  [91mERROR:  Error installing rubocop:
15:30:43  	parallel requires Ruby version >= 2.5.
15:30:43  [0mSuccessfully installed jaro_winkler-1.5.4
15:30:44  The command '/bin/sh -c gem install rubocop:'<= 0.81'' returned a non-zero code: 1
15:30:44  ERROR: Docker failed to build yetus/hbase:b249092a5f.