Make all exceptions implement a common interface

src/Exception/EtcdException.php

@@ -7,6 +7,6 @@
 /**
  * @author Cong Peijun <[email protected]>
  */
-class EtcdException extends Exception
+class EtcdException extends Exception implements ExceptionInterface
 {
 }

src/Exception/ExceptionInterface.php

@@ -0,0 +1,10 @@
+<?php
+
+namespace ActiveCollab\Etcd\Exception;
+
+/**
+ * @package ActiveCollab\Etcd\Exception
+ */
+interface ExceptionInterface
+{
+}

src/Exception/KeyExistsException.php

@@ -5,6 +5,6 @@
 /**
  * @author Cong Peijun <[email protected]>
  */
-class KeyExistsException extends EtcdException
+class KeyExistsException extends EtcdException implements ExceptionInterface
 {
 }

src/Exception/KeyNotFoundException.php

@@ -5,6 +5,6 @@
 /**
  * @author Cong Peijun <[email protected]>
  */
-class KeyNotFoundException extends EtcdException
+class KeyNotFoundException extends EtcdException implements ExceptionInterface
 {
 }