[rubygems/rubygems] Fix error handling of #with_engine_version

* If settings constants fail, show that exception instead of getting
  another one due to variables being unset and hiding the real cause.

https://github.com/rubygems/rubygems/commit/f38cd67874

test/rubygems/test_gem_request_set_gem_dependency_api.rb

@@ -34,8 +34,8 @@ class TestGemRequestSetGemDependencyAPI < Gem::TestCase
 
     Gem.instance_variable_set :@ruby_version, Gem::Version.new(version)
 
+    begin
       yield
-
     ensure
       Object.send :remove_const, :RUBY_ENGINE             if name
       Object.send :remove_const, new_engine_version_const if version
@@ -50,6 +50,7 @@ class TestGemRequestSetGemDependencyAPI < Gem::TestCase
       Gem.send :remove_instance_variable, :@ruby_version if
         Gem.instance_variables.include? :@ruby_version
     end
+  end
 
   def test_gempspec_with_multiple_runtime_deps
     save_gemspec 'foo', '1.0' do |s|