[rubygems/rubygems] Remove unnecessary DIR constant

We have `__dir__` which is the same thing.

rubygems/rubygems@f89776427f

test/rubygems/test_gem_remote_fetcher.rb

@@ -78,8 +78,6 @@ class TestGemRemoteFetcher < Gem::TestCase
 
   PROXY_DATA = SERVER_DATA.gsub(/0.4.11/, '0.4.2')
 
-  DIR = File.expand_path(File.dirname(__FILE__))
-
   # Generated via:
   #   x = OpenSSL::PKey::DH.new(2048) # wait a while...
   #   x.to_s => pem
@@ -890,7 +888,7 @@ def test_yaml_error_on_size
 
   def test_ssl_connection
     ssl_server = start_ssl_server
-    temp_ca_cert = File.join(DIR, 'ca_cert.pem')
+    temp_ca_cert = File.join(__dir__, 'ca_cert.pem')
     with_configured_fetcher(":ssl_ca_cert: #{temp_ca_cert}") do |fetcher|
       fetcher.fetch_path("https://localhost:#{ssl_server.config[:Port]}/yaml")
     end
@@ -901,8 +899,8 @@ def test_ssl_client_cert_auth_connection
       :SSLVerifyClient =>
         OpenSSL::SSL::VERIFY_PEER | OpenSSL::SSL::VERIFY_FAIL_IF_NO_PEER_CERT})
 
-    temp_ca_cert = File.join(DIR, 'ca_cert.pem')
-    temp_client_cert = File.join(DIR, 'client.pem')
+    temp_ca_cert = File.join(__dir__, 'ca_cert.pem')
+    temp_client_cert = File.join(__dir__, 'client.pem')
 
     with_configured_fetcher(
       ":ssl_ca_cert: #{temp_ca_cert}\n" +
@@ -916,8 +914,8 @@ def test_do_not_allow_invalid_client_cert_auth_connection
       :SSLVerifyClient =>
         OpenSSL::SSL::VERIFY_PEER | OpenSSL::SSL::VERIFY_FAIL_IF_NO_PEER_CERT})
 
-    temp_ca_cert = File.join(DIR, 'ca_cert.pem')
-    temp_client_cert = File.join(DIR, 'invalid_client.pem')
+    temp_ca_cert = File.join(__dir__, 'ca_cert.pem')
+    temp_client_cert = File.join(__dir__, 'invalid_client.pem')
 
     with_configured_fetcher(
       ":ssl_ca_cert: #{temp_ca_cert}\n" +
@@ -946,7 +944,7 @@ def test_ssl_connection_allow_verify_none
 
   def test_do_not_follow_insecure_redirect
     ssl_server = start_ssl_server
-    temp_ca_cert = File.join(DIR, 'ca_cert.pem')
+    temp_ca_cert = File.join(__dir__, 'ca_cert.pem')
     expected_error_message =
       "redirecting to non-https resource: #{@server_uri} (https://localhost:#{ssl_server.config[:Port]}/insecure_redirect?to=#{@server_uri})"
 
@@ -1055,16 +1053,14 @@ def proxy_server_port
     @proxy_server[:server].config[:Port]
   end
 
-  DIR = File.expand_path(File.dirname(__FILE__))
-
   def start_ssl_server(config = {})
     null_logger = NilLog.new
     server = WEBrick::HTTPServer.new({
       :Port => 0,
       :Logger => null_logger,
       :AccessLog => [],
       :SSLEnable => true,
-      :SSLCACertificateFile => File.join(DIR, 'ca_cert.pem'),
+      :SSLCACertificateFile => File.join(__dir__, 'ca_cert.pem'),
       :SSLCertificate => cert('ssl_cert.pem'),
       :SSLPrivateKey => key('ssl_key.pem'),
       :SSLVerifyClient => nil,
@@ -1145,11 +1141,11 @@ def start_server(data)
   end
 
   def cert(filename)
-    OpenSSL::X509::Certificate.new(File.read(File.join(DIR, filename)))
+    OpenSSL::X509::Certificate.new(File.read(File.join(__dir__, filename)))
   end
 
   def key(filename)
-    OpenSSL::PKey::RSA.new(File.read(File.join(DIR, filename)))
+    OpenSSL::PKey::RSA.new(File.read(File.join(__dir__, filename)))
   end
 
 end if defined?(OpenSSL::SSL)