Promote warn_unknown_analyzer_checker to an error.  Addresses <rdar://problem/10987863>.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@160706 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/StaticAnalyzer/Frontend/CheckerRegistration.cpp b/lib/StaticAnalyzer/Frontend/CheckerRegistration.cpp
index c06da0d..0229aed 100644
--- a/lib/StaticAnalyzer/Frontend/CheckerRegistration.cpp
+++ b/lib/StaticAnalyzer/Frontend/CheckerRegistration.cpp
@@ -118,7 +118,7 @@
 
   for (unsigned i = 0, e = checkerOpts.size(); i != e; ++i) {
     if (checkerOpts[i].isUnclaimed())
-      diags.Report(diag::warn_unknown_analyzer_checker)
+      diags.Report(diag::err_unknown_analyzer_checker)
           << checkerOpts[i].getName();
   }