[rubygems/rubygems] Enhance error handling when loading the rubygems/defaults/operating_system file

When loading `rubygems/defaults/operating_system`
- we want to keep it silent if the raised exception is a LoadError
- we want to print a message in other cases and ask users to report the issue to their OS support.

Ruby 3 comes with special error handling for loading `rubygems` and it will show a warning when LoadError exception raised for requiring 'rubygem'.
Because of that, we decided to leave the LoadError scenario as it is.
Reference: d1998d8767/gem_prelude.rb (L1-L5)

https://github.com/rubygems/rubygems/commit/0a97e12fe1

lib/rubygems.rb

@@ -1331,6 +1331,9 @@ begin
 
   require 'rubygems/defaults/operating_system'
 rescue LoadError
+  # Ignored
+rescue Exception => e
+  raise e.class, "#{e.message}\nThis is not expected so please report this issue to your OS support and ask for help."
 end
 
 begin

test/rubygems/test_rubygems.rb

@@ -0,0 +1,38 @@
+require_relative 'helper'
+
+class GemTest < Gem::TestCase
+  def test_rubygems_normal_behaviour
+    _ = Gem::Util.popen(*ruby_with_rubygems_in_load_path, '-e', "'require \"rubygems\"'", {:err => [:child, :out]}).strip
+    assert $?.success?
+  end
+
+  def test_operating_system_other_exceptions
+    path = util_install_operating_system_rb <<-RUBY
+      intentional synt'ax error
+    RUBY
+
+    output = Gem::Util.popen(*ruby_with_rubygems_and_fake_operating_system_in_load_path(path), '-e', "'require \"rubygems\"'", {:err => [:child, :out]}).strip
+    assert !$?.success?
+    assert_includes output, "This is not expected so please report this issue to your OS support and ask for help"
+  end
+
+  private
+
+  def util_install_operating_system_rb(content)
+    dir_lib = Dir.mktmpdir("test_operating_system_lib", @tempdir)
+    dir_lib_arg = File.join dir_lib
+
+    dir_lib_rubygems_defaults_arg = File.join dir_lib_arg, "lib", "rubygems", "defaults"
+    FileUtils.mkdir_p dir_lib_rubygems_defaults_arg
+
+    operating_system_rb = File.join dir_lib_rubygems_defaults_arg, "operating_system.rb"
+
+    File.open(operating_system_rb, 'w') {|f| f.write content }
+
+    File.join dir_lib_arg, "lib"
+  end
+
+  def ruby_with_rubygems_and_fake_operating_system_in_load_path(operating_system_path)
+    [Gem.ruby, "-I", operating_system_path, "-I" , $LOAD_PATH.find{|p| p == File.dirname($LOADED_FEATURES.find{|f| f.end_with?("/rubygems.rb") }) }]
+  end
+end