Switch the "no module found" default-fatal warning to a default-fatal error.

llvm-svn: 138909
diff --git a/clang/lib/Frontend/CompilerInstance.cpp b/clang/lib/Frontend/CompilerInstance.cpp
index f53d0b0..344e77b 100644
--- a/clang/lib/Frontend/CompilerInstance.cpp
+++ b/clang/lib/Frontend/CompilerInstance.cpp
@@ -645,7 +645,7 @@
                                            /*SearchPath=*/0, 
                                            /*RelativePath=*/0);
   if (!ModuleFile) {
-    getDiagnostics().Report(ModuleNameLoc, diag::warn_module_not_found)
+    getDiagnostics().Report(ModuleNameLoc, diag::err_module_not_found)
       << ModuleName.getName()
       << SourceRange(ImportLoc, ModuleNameLoc);
     return 0;