Improve ext/session error messages
diff --git a/system/libraries/Session/Session_driver.php b/system/libraries/Session/Session_driver.php
index 98fc897..55ddb25 100644
--- a/system/libraries/Session/Session_driver.php
+++ b/system/libraries/Session/Session_driver.php
@@ -168,4 +168,24 @@
 		return TRUE;
 	}
 
+	// ------------------------------------------------------------------------
+
+	/**
+	 * Fail
+	 *
+	 * Drivers other than the 'files' one don't (need to) use the
+	 * session.save_path INI setting, but that leads to confusing
+	 * error messages emitted by PHP when open() or write() fail,
+	 * as the message contains session.save_path ...
+	 * To work around the problem, the drivers will call this method
+	 * so that the INI is set just in time for the error message to
+	 * be properly generated.
+	 *
+	 * @return	mixed
+	 */
+	protected function _fail()
+	{
+		ini_set('session.save_path', config_item('sess_save_path'));
+		return $this->_failure;
+	}
 }