✅ Add new exceptions

src/Exception/ChannelNotFoundInRSSException.php

@@ -0,0 +1,12 @@
+<?php
+
+namespace Shikiryu\SRSS\Exception;
+
+class ChannelNotFoundInRSSException extends SRSSException
+{
+    public function __construct($file)
+    {
+        parent::__construct(sprintf('Invalid file `%s`: <channel> not found', $file));
+    }
+
+}

src/Exception/PropertyNotFoundException.php

@@ -0,0 +1,15 @@
+<?php
+
+namespace Shikiryu\SRSS\Exception;
+
+class PropertyNotFoundException extends SRSSException
+{
+    /**
+     * @param string $class
+     * @param string $name
+     */
+    public function __construct($class, $name)
+    {
+        parent::__construct(sprintf('Property `%s` not found in `%s`', $name, $class));
+    }
+}

src/Exception/UnreadableRSSException.php

@@ -0,0 +1,12 @@
+<?php
+
+namespace Shikiryu\SRSS\Exception;
+
+class UnreadableRSSException extends SRSSException
+{
+    public function __construct($file)
+    {
+        parent::__construct(sprintf('File `%s` is unreadable.', $file));
+    }
+
+}