Merge branch '3.4' into 4.3

* 3.4:
  add missing blank line
  Add caution about combining excluded_404s with passthru_level

Author: OskarStark

logging/monolog_regex_based_excludes.rst

@@ -66,3 +66,13 @@ configuration:
                 ],
             ],
         ]);
+
+
+.. caution::
+
+    Combining ``excluded_404s`` with a ``passthru_level`` lower than
+    ``error`` (i.e. ``debug``, ``info``, ``notice`` or ``warning``) will not
+    actually exclude log messages for the URL(s) listed in ``excluded_404s``
+    because they are logged with level of ``error`` or higher and
+    ``passthru_level`` takes precedence over the URLs being listed in
+    ``excluded_404s``.