diff --git a/Lib/http/server.py b/Lib/http/server.py
index 09fa44c..193964f 100644
--- a/Lib/http/server.py
+++ b/Lib/http/server.py
@@ -883,6 +883,9 @@
         (dir, rest) if self.path requires running a CGI script.
         Returns False otherwise.
 
+        If any exception is raised, the caller should assume that
+        self.path was rejected as invalid and act accordingly.
+
         The default implementation tests whether the normalized url
         path begins with one of the strings in self.cgi_directories
         (and the next character is a '/' or the end of the string).