Check the output name is not fixed when there are several videos to download

youtube-dl

@@ -38,7 +38,7 @@ class FileDownloader(object):
 	For this, file downloader objects have a method that allows
 	InfoExtractors to be registered in a given order. When it is passed
 	a URL, the file downloader handles it to the first InfoExtractor it
-	finds that reports it's able to handle it. The InfoExtractor returns
+	finds that reports being able to handle it. The InfoExtractor returns
 	all the information to the FileDownloader and the latter downloads the
 	file or does whatever it's instructed to do.
 
@@ -153,9 +153,12 @@ class FileDownloader(object):
 					continue
 				# Suitable InfoExtractor found
 				suitable_found = True
-				for result in ie.extract(url):
-					if result is None:
-						continue
+				results = [x for x in ie.extract(url) if x is not None]
+
+				if (len(url_list) > 1 or len(results) > 1) and re.search(r'%\(.+?\)s', self._params['outtmpl']) is None:
+					sys.exit('ERROR: fixed output name but more than one file to download')
+
+				for result in results:
 					try:
 						filename = self._params['outtmpl'] % result
 					except (KeyError), err: