Fix handling of format strings to work with python 2.6

llvm-svn: 216314
diff --git a/libcxx/test/lit.cfg b/libcxx/test/lit.cfg
index e37e641..4fc082a 100644
--- a/libcxx/test/lit.cfg
+++ b/libcxx/test/lit.cfg
@@ -307,9 +307,9 @@
         for feature, loc in locales[platform.system()].items():
             try:
                 locale.setlocale(locale.LC_ALL, loc)
-                self.config.available_features.add('locale.{}'.format(feature))
+                self.config.available_features.add('locale.{0}'.format(feature))
             except:
-                self.lit_config.warning('The locale {} is not supported by '
+                self.lit_config.warning('The locale {0} is not supported by '
                                         'your platform. Some tests will be '
                                         'unsupported.'.format(loc))
         locale.setlocale(locale.LC_ALL, default_locale)
@@ -384,7 +384,7 @@
         if std is None:
             std = 'c++11'
             self.lit_config.note('using default std: \'-std=c++11\'')
-        self.compile_flags += ['-std={}'.format(std)]
+        self.compile_flags += ['-std={0}'.format(std)]
         self.config.available_features.add(std)
 
     def configure_sanitizer(self):
@@ -401,7 +401,7 @@
                 self.config.available_features.add('msan')
             else:
                 self.lit_config.fatal('unsupported value for '
-                                      'libcxx_use_san: {}'.format(san))
+                                      'libcxx_use_san: {0}'.format(san))
 
     def configure_triple(self):
         # Get or infer the target triple.