Cleanups in distutils tests.

- Actually check the contents of the file created by bdist_dumb.
- Don’t use “RECORD” as filename for non-PEP 376 record file
- Don’t start method name with “_test”, it smells like a disabled test
  method instead of an helper method
- Fix some idioms (assertIn, addCleanup)

Lib/distutils/tests/test_sdist.py

@@ -288,7 +288,7 @@ class SDistTestCase(PyPIRCCommandTestCase):
     # the following tests make sure there is a nice error message instead
     # of a traceback when parsing an invalid manifest template
 
-    def _test_template(self, content):
+    def _check_template(self, content):
         dist, cmd = self.get_cmd()
         os.chdir(self.tmp_dir)
         self.write_file('MANIFEST.in', content)
@@ -299,17 +299,17 @@ class SDistTestCase(PyPIRCCommandTestCase):
         self.assertEqual(len(warnings), 1)
 
     def test_invalid_template_unknown_command(self):
-        self._test_template('taunt knights *')
+        self._check_template('taunt knights *')
 
     def test_invalid_template_wrong_arguments(self):
         # this manifest command takes one argument
-        self._test_template('prune')
+        self._check_template('prune')
 
     @unittest.skipIf(os.name != 'nt', 'test relevant for Windows only')
     def test_invalid_template_wrong_path(self):
         # on Windows, trailing slashes are not allowed
         # this used to crash instead of raising a warning: #8286
-        self._test_template('include examples/')
+        self._check_template('include examples/')
 
     @unittest.skipUnless(ZLIB_SUPPORT, 'Need zlib support to run')
     def test_get_file_list(self):