Add an inspirational quote.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@111641 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/Support/raw_ostream.h

@@ -382,6 +382,11 @@ public:
   /// flag is set at the time when this raw_ostream's destructor is called,
   /// report_fatal_error is called to report the error. Use clear_error()
   /// after handling the error to avoid this behavior.
+  ///
+  ///   "Errors should never pass silently.
+  ///    Unless explicitly silenced."
+  ///      - from The Zen of Python, by Tim Peters
+  ///
   void clear_error() {
     Error = false;
   }