[YoutubeDL] Add playlist finished downloading message (Closes #7517)

Conflicts:
	youtube_dl/YoutubeDL.py

youtube_dl/YoutubeDL.py

@@ -833,6 +833,7 @@ class YoutubeDL(object):
                                                       extra_info=extra)
                 playlist_results.append(entry_result)
             ie_result['entries'] = playlist_results
+            self.to_screen('[download] Finished downloading playlist: %s' % playlist)
             return ie_result
         elif result_type == 'compat_list':
             self.report_warning(