Vinay, this patch introduces regressions.

You can either revert this part:

--- a/Lib/distutils/cmd.py
+++ b/Lib/distutils/cmd.py
@@ -329,8 +329,7 @@ class Command:
     # -- External world manipulation -----------------------------------

     def warn(self, msg):
-        log.warn("warning: %s: %s\n" %
-                (self.get_command_name(), msg))
+        log.warn("warning: %s: %s\n", self.get_command_name(), msg)

     def execute(self, func, args, msg=None, level=1):
         util.execute(func, args, msg, dry_run=self.dry_run)

or change the test suites to:

diff -r 1340e298aa7e Lib/distutils/tests/test_build_py.py
--- a/Lib/distutils/tests/test_build_py.py	Wed Aug 31 08:22:29 2016 +0100
+++ b/Lib/distutils/tests/test_build_py.py	Wed Aug 31 16:59:27 2016 +0800
@@ -168,7 +168,8 @@
         finally:
             sys.dont_write_bytecode = old_dont_write_bytecode
 
-        self.assertIn('byte-compiling is disabled', self.logs[0][1])
+        self.assertIn('byte-compiling is disabled',
+                      self.logs[0][1] % self.logs[0][2])
 
 
 def test_suite():
diff -r 1340e298aa7e Lib/distutils/tests/test_install_lib.py
--- a/Lib/distutils/tests/test_install_lib.py	Wed Aug 31 08:22:29 2016 +0100
+++ b/Lib/distutils/tests/test_install_lib.py	Wed Aug 31 16:59:27 2016 +0800
@@ -104,7 +104,8 @@
         finally:
             sys.dont_write_bytecode = old_dont_write_bytecode
 
-        self.assertIn('byte-compiling is disabled', self.logs[0][1])
+        self.assertIn('byte-compiling is disabled',
+                      self.logs[0][1] % self.logs[0][2])
 
 
 def test_suite():