Add changelog entry.

docs/news.rst

@@ -8,6 +8,7 @@ Lab
 ^^^
 * Allow passing properties files to fetchers directly (Jendrik Seipp).
 * Let fetch and report steps log only the total number of unexplained errors instead of printing all of them to stderr (Jendrik Seipp).
+* Let parsers abort with an error if the file for a required pattern is missing. Parsers do not print anything if a file used by a function or non-required patterns is missing (Silvan Sievers).
 
 Downward Lab
 ^^^^^^^^^^^^