Add 100% line/branch coverage to rack/builder.rb

Change error message for .ru file with embedded options, since it's not
just deprecated, the support has been fully removed.

Coverage after this commit:

3282 relevant lines, 3282 lines covered and 0 lines missed. ( 100.0% )
1110 total branches, 1068 branches covered and 42 branches missed. ( 96.22% )

2 files changed, 10 insertions, 1 deletions

diff --git a/lib/rack/builder.rb b/lib/rack/builder.rb
index b85eb8ed..992bf059 100644
--- a/lib/rack/builder.rb
+++ b/lib/rack/builder.rb
@@ -88,7 +88,7 @@ module Rack
       config.slice!(/\A#{UTF_8_BOM}/) if config.encoding == Encoding::UTF_8
 
       if config[/^#\\(.*)/]
-        fail "Parsing options from the first comment line is deprecated: #{path}"
+        fail "Parsing options from the first comment line is no longer supported: #{path}"
       end
 
       config.sub!(/^__END__\n.*\Z/m, '')
@@ -152,7 +152,9 @@ module Rack
       end
       @use << proc { |app| middleware.new(app, *args, &block) }
     end
+    # :nocov:
     ruby2_keywords(:use) if respond_to?(:ruby2_keywords, true)
+    # :nocov:
 
     # Takes an argument that is an object that responds to #call and returns a Rack response.
     # The simplest form of this is a lambda object:
diff --git a/test/spec_builder.rb b/test/spec_builder.rb
index 5cea34a3..3b02bcc1 100644
--- a/test/spec_builder.rb
+++ b/test/spec_builder.rb
@@ -238,6 +238,13 @@ describe Rack::Builder do
       File.join(File.dirname(__FILE__), 'builder', name)
     end
 
+    it "raises if parses commented options" do
+      proc do
+        Rack::Builder.parse_file config_file('options.ru')
+      end.must_raise(RuntimeError).
+       message.must_include('Parsing options from the first comment line is no longer supported')
+    end
+
     it "removes __END__ before evaluating app" do
       app, _ = Rack::Builder.parse_file config_file('end.ru')
       Rack::MockRequest.new(app).get("/").body.to_s.must_equal 'OK'