bridges: Don't kill scripts with die()

Bridges should generally utilize the API functions instead of killing
the script. Find more information on the Wiki.

- returnServerError
https://github.com/RSS-Bridge/rss-bridge/wiki/The-returnServerError-function

- returnClientError
https://github.com/RSS-Bridge/rss-bridge/wiki/The-returnClientError-function

- returnError
https://github.com/RSS-Bridge/rss-bridge/wiki/The-returnError-function

bridges/Arte7Bridge.php

@@ -91,7 +91,8 @@ class Arte7Bridge extends BridgeAbstract {
 			'Authorization: Bearer ' . self::API_TOKEN
 		);
 
-		$input = getContents($url, $header) or die('Could not request ARTE.');
+		$input = getContents($url, $header)
+			or returnServerError('Could not request ARTE.');
 		$input_json = json_decode($input, true);
 
 		foreach($input_json['videos'] as $element) {