[rubygems/rubygems] Remove the warning for not defining a gem server source

Bundler has deprecated gemfiles without a global source and this feature
is now obsolete. `Bundler::Definition#has_rubygems_remotes?` is removed
because it's not used anymore.

https://github.com/rubygems/rubygems/commit/d29dd2cb7b

lib/bundler/cli/install.rb

@@ -83,18 +83,11 @@ module Bundler
       end
 
       Bundler::CLI::Common.output_fund_metadata_summary
-    rescue GemNotFound, VersionConflict => e
+    rescue GemNotFound => e
       if options[:local] && Bundler.app_cache.exist?
         Bundler.ui.warn "Some gems seem to be missing from your #{Bundler.settings.app_cache_path} directory."
       end
 
-      unless Bundler.definition.has_rubygems_remotes?
-        Bundler.ui.warn <<-WARN, :wrap => true
-          Your Gemfile has no gem server sources. If you need gems that are \
-          not already on your machine, add a line like this to your Gemfile:
-          source 'https://rubygems.org'
-        WARN
-      end
       raise e
     rescue Gem::InvalidSpecificationException => e
       Bundler.ui.warn "You have one or more invalid gemspecs that need to be fixed."

lib/bundler/definition.rb

@@ -279,10 +279,6 @@ module Bundler
       end
     end
 
-    def has_rubygems_remotes?
-      sources.rubygems_sources.any? {|s| s.remotes.any? }
-    end
-
     def spec_git_paths
       sources.git_sources.map {|s| File.realpath(s.path) if File.exist?(s.path) }.compact
     end

spec/bundler/commands/install_spec.rb

@@ -331,11 +331,13 @@ RSpec.describe "bundle install with gem sources" do
 
     it "gives a useful error if no sources are set" do
       install_gemfile <<-G, :raise_on_error => false
-        source "#{file_uri_for(gem_repo1)}"
         gem "rack"
       G
 
-      expect(err).to include("Your Gemfile has no gem server sources")
+      expect(err).to include("This Gemfile does not include an explicit global source. " \
+        "Not using an explicit global source may result in a different lockfile being generated depending on " \
+        "the gems you have installed locally before bundler is run." \
+        "Instead, define a global source in your Gemfile like this: source \"https://rubygems.org\".")
     end
 
     it "creates a Gemfile.lock on a blank Gemfile" do