Rails 5.2 + Ruby 2.5.1 via rbenv warnings.

console.log

rails s                                                                                                                  08:49:35
/Users/bijan/.rbenv/versions/2.5.1/lib/ruby/2.5.0/fileutils.rb:90: warning: already initialized constant FileUtils::VERSION
/Users/bijan/.rbenv/versions/2.5.1/lib/ruby/gems/2.5.0/gems/fileutils-1.1.0/lib/fileutils.rb:92: warning: previous definition of VERSION was here
/Users/bijan/.rbenv/versions/2.5.1/lib/ruby/2.5.0/fileutils.rb:1188: warning: already initialized constant FileUtils::Entry_::S_IF_DOOR
/Users/bijan/.rbenv/versions/2.5.1/lib/ruby/gems/2.5.0/gems/fileutils-1.1.0/lib/fileutils.rb:1267: warning: previous definition of S_IF_DOOR was here
/Users/bijan/.rbenv/versions/2.5.1/lib/ruby/2.5.0/fileutils.rb:1446: warning: already initialized constant FileUtils::Entry_::DIRECTORY_TERM
/Users/bijan/.rbenv/versions/2.5.1/lib/ruby/gems/2.5.0/gems/fileutils-1.1.0/lib/fileutils.rb:1541: warning: previous definition of DIRECTORY_TERM was here
/Users/bijan/.rbenv/versions/2.5.1/lib/ruby/2.5.0/fileutils.rb:1448: warning: already initialized constant FileUtils::Entry_::SYSCASE
/Users/bijan/.rbenv/versions/2.5.1/lib/ruby/gems/2.5.0/gems/fileutils-1.1.0/lib/fileutils.rb:1543: warning: previous definition of SYSCASE was here
/Users/bijan/.rbenv/versions/2.5.1/lib/ruby/2.5.0/fileutils.rb:1501: warning: already initialized constant FileUtils::OPT_TABLE
/Users/bijan/.rbenv/versions/2.5.1/lib/ruby/gems/2.5.0/gems/fileutils-1.1.0/lib/fileutils.rb:1596: warning: previous definition of OPT_TABLE was here
/Users/bijan/.rbenv/versions/2.5.1/lib/ruby/2.5.0/fileutils.rb:1555: warning: already initialized constant FileUtils::LOW_METHODS
/Users/bijan/.rbenv/versions/2.5.1/lib/ruby/gems/2.5.0/gems/fileutils-1.1.0/lib/fileutils.rb:1650: warning: previous definition of LOW_METHODS was here
/Users/bijan/.rbenv/versions/2.5.1/lib/ruby/2.5.0/fileutils.rb:1562: warning: already initialized constant FileUtils::METHODS
/Users/bijan/.rbenv/versions/2.5.1/lib/ruby/gems/2.5.0/gems/fileutils-1.1.0/lib/fileutils.rb:1657: warning: previous definition of METHODS was here
=> Booting Puma
=> Rails 5.2.0 application starting in development 
=> Run `rails server -h` for more startup options
Puma starting in single mode...
* Version 3.11.4 (ruby 2.5.1-p57), codename: Love Song
* Min threads: 5, max threads: 5
* Environment: development
* Listening on tcp://0.0.0.0:3000
Use Ctrl-C to stop

I'm running into this too, did you find a fix?

Found a fix at stackoverflow last night.
https://stackoverflow.com/a/51770374/9031758