Fix distutils byte-compilation to comply with PEP 3147 (#11254).

Patch by Jeff Ramnani.  Tested with -B, -O and -OO.
diff --git a/Lib/distutils/tests/test_install_lib.py b/Lib/distutils/tests/test_install_lib.py
index fddaabe..b42b03b 100644
--- a/Lib/distutils/tests/test_install_lib.py
+++ b/Lib/distutils/tests/test_install_lib.py
@@ -1,6 +1,7 @@
 """Tests for distutils.command.install_data."""
 import sys
 import os
+import imp
 import unittest
 
 from distutils.command.install_lib import install_lib
@@ -32,18 +33,20 @@
         cmd.finalize_options()
         self.assertEqual(cmd.optimize, 2)
 
-    @unittest.skipUnless(not sys.dont_write_bytecode,
-                         'byte-compile not supported')
+    @unittest.skipIf(sys.dont_write_bytecode, 'byte-compile disabled')
     def test_byte_compile(self):
         pkg_dir, dist = self.create_dist()
+        os.chdir(pkg_dir)
         cmd = install_lib(dist)
         cmd.compile = cmd.optimize = 1
 
         f = os.path.join(pkg_dir, 'foo.py')
         self.write_file(f, '# python file')
         cmd.byte_compile([f])
-        self.assertTrue(os.path.exists(os.path.join(pkg_dir, 'foo.pyc')))
-        self.assertTrue(os.path.exists(os.path.join(pkg_dir, 'foo.pyo')))
+        pyc_file = imp.cache_from_source('foo.py')
+        pyo_file = imp.cache_from_source('foo.py', debug_override=False)
+        self.assertTrue(os.path.exists(pyc_file))
+        self.assertTrue(os.path.exists(pyo_file))
 
     def test_get_outputs(self):
         pkg_dir, dist = self.create_dist()