Fix dependencies for Ruby head

draper.gemspec

@@ -53,6 +53,7 @@ Gem::Specification.new do |s|
     s.add_development_dependency "bigdecimal"
     s.add_development_dependency "mutex_m"
     s.add_development_dependency "drb"
+    s.add_development_dependency "logger"
   end
   # rubocop:enable Gemspec/RubyVersionGlobalsUsage
 end