Ruby 2.5.0 breaks rmate

[caffeineflo]

rmate used to work on all my server for years without any issues, now recently after having to upgrade to Ruby 2.5.0 and the rubygems system, rmate stopped working with the following error message:

connect_to localhost: unknown host (nodename nor servname provided, or not known)
Traceback (most recent call last):
	6: from /root/.gem/ruby/2.5.0/bin/rmate:23:in `<main>'
	5: from /root/.gem/ruby/2.5.0/bin/rmate:23:in `load'
	4: from /root/.gem/ruby/2.5.0/gems/rmate-1.5.9/bin/rmate:222:in `<top (required)>'
	3: from /root/.gem/ruby/2.5.0/gems/rmate-1.5.9/bin/rmate:222:in `fork'
	2: from /root/.gem/ruby/2.5.0/gems/rmate-1.5.9/bin/rmate:223:in `block in <top (required)>'
	1: from /root/.gem/ruby/2.5.0/gems/rmate-1.5.9/bin/rmate:174:in `connect_and_handle_cmds'
/root/.gem/ruby/2.5.0/gems/rmate-1.5.9/bin/rmate:174:in `readline': end of file reached (EOFError)

Looking at the error message it seems like localhost couldn't resolve, but changing to 127.0.0.1 didn't help and it's widespread for me over all my server.

[caffeineflo]

My bad, my hosts file on my MacBook was empty after the latest migration to newer hardware. Thanks Apple Migration Assistant ...