Ruby

[ruby/irb] Warn users about errors in loading RC files
(https://github.com/ruby/irb/pull/817)

1. Because IRB.rc_file always generates an rc file name, even if the
   file doesn't exist, we should check the file exists before trying to
   load it.
2. If any type of errors occur while loading the rc file, we should
   warn the user about it.

https://github.com/ruby/irb/commit/37ffdc6b19