diff -r 1bc0a8310b9f Lib/_osx_support.py
--- a/Lib/_osx_support.py	Thu Apr 17 20:11:19 2014 +0200
+++ b/Lib/_osx_support.py	Sat Apr 19 09:09:15 2014 -0400
@@ -182,7 +182,7 @@
         # Compiler is GCC, check if it is LLVM-GCC
         data = _read_output("'%s' --version"
                              % (cc.replace("'", "'\"'\"'"),))
-        if 'llvm-gcc' in data:
+        if data and 'llvm-gcc' in data:
             # Found LLVM-GCC, fall back to clang
             cc = _find_build_tool('clang')