Added a missing use clause in test

Signed-off-by: Ivan Habunek <ivan.habunek@gmail.com>

tests/src/Appenders/SocketAppenderTest.php

diff --git a/tests/src/Appenders/SocketAppenderTest.php b/tests/src/Appenders/SocketAppenderTest.php
index 6a26251..eb33d6c 100644
--- a/tests/src/Appenders/SocketAppenderTest.php
+++ b/tests/src/Appenders/SocketAppenderTest.php
@@ -25,6 +25,8 @@
 use Apache\Log4php\Appenders\SocketAppender;
 use Apache\Log4php\Logger;
 
+use Exception;
+
 /**
  * @group appenders
  */