Raise Net::LDAP::ConnectionRefusedError when new connection is refused.

Now Net::LDAP::Connection.new raises Net::LDAP::Error even if the
connection refused.

It's hard for some application to reconnect it only when refused.

Author: satoryu

lib/net/ldap/connection.rb

@@ -14,7 +14,7 @@ def initialize(server)
     rescue SocketError
       raise Net::LDAP::Error, "No such address or other socket error."
     rescue Errno::ECONNREFUSED
-      raise Net::LDAP::Error, "Server #{server[:host]} refused connection on port #{server[:port]}."
+      raise Net::LDAP::ConnectionRefusedError, "Server #{server[:host]} refused connection on port #{server[:port]}."
     rescue Errno::EHOSTUNREACH => error
       raise Net::LDAP::Error, "Host #{server[:host]} was unreachable (#{error.message})"
     rescue Errno::ETIMEDOUT

test/test_ldap_connection.rb

@@ -14,6 +14,13 @@ def test_blocked_port
     end
   end
 
+  def test_connection_refused
+    flexmock(TCPSocket).should_receive(:new).and_raise(Errno::ECONNREFUSED)
+    assert_raise Net::LDAP::ConnectionRefusedError do
+      Net::LDAP::Connection.new(:host => 'test.mocked.com', :port => 636)
+    end
+  end
+
   def test_raises_unknown_exceptions
     error = Class.new(StandardError)
     flexmock(TCPSocket).should_receive(:new).and_raise(error)