It seems that ruby_parser version > 3.1.1 is breaking with latest safemode (1.2.1)
The issue may be with safemode gem
(tried running:

ruby ~/.rvm/gems/ruby-2.0.0-p576/gems/safemode-1.2.1/demo.rb 

)
and got:

Safemode doesn't allow to access 'constant' on Encoding (Safemode::SecurityError)

which is also breaking our tests when using ruby_parser version 3.6.3