Fixes a bug in testing code handling .pth files that did not restore the original

module that is removed for testing "import" lines.  Originally deleted the
entry from sys.modules and then just let other code that needed it to import it
again.  Problem with this solution is that it lead to code that had already
imported the module in question to have their own reference to a new copy of
the module in question that new code couldn't reach.  This lead to a failure in
test_strptime since it monkey-patched the 'time' module it had a reference to
while _strptime had its own reference to another copy of 'time' from being
imported by test___all__ that it was using for a calculation.

Also moved the testing code out of the PthFile class and into the actual test
class.  This was to stop using 'assert' which is useless with a -O execution.

Lib/test/test_site.py

@@ -56,18 +56,25 @@ class HelperFunctionsTests(unittest.TestCase):
                             "%s from sys.path not found in set returned "
                             "by _init_pathinfo(): %s" % (entry, dir_set))
 
+    def pth_file_tests(self, pth_file):
+        """Contain common code for testing results of reading a .pth file"""
+        self.failUnless(pth_file.imported in sys.modules,
+                "%s not in sys.path" % pth_file.imported)
+        self.failUnless(site.makepath(pth_file.good_dir_path)[0] in sys.path)
+        self.failUnless(not os.path.exists(pth_file.bad_dir_path))
+
     def test_addpackage(self):
         # Make sure addpackage() imports if the line starts with 'import',
         # adds directories to sys.path for any line in the file that is not a
         # comment or import that is a valid directory name for where the .pth
         # file resides; invalid directories are not added
         pth_file = PthFile()
-        pth_file.cleanup()  # to make sure that nothing is pre-existing that
-                            # shouldn't be
+        pth_file.cleanup(prep=True)  # to make sure that nothing is
+                                      # pre-existing that shouldn't be
         try:
             pth_file.create()
             site.addpackage(pth_file.base_dir, pth_file.filename, set())
-            unittest.FunctionTestCase(pth_file.test)
+            self.pth_file_tests(pth_file)
         finally:
             pth_file.cleanup()
 
@@ -75,11 +82,12 @@ class HelperFunctionsTests(unittest.TestCase):
         # Same tests for test_addpackage since addsitedir() essentially just
         # calls addpackage() for every .pth file in the directory
         pth_file = PthFile()
-        pth_file.cleanup() # Make sure that nothing is pre-existing that is
-                           # tested for
+        pth_file.cleanup(prep=True) # Make sure that nothing is pre-existing
+                                    # that is tested for
         try:
+            pth_file.create()
             site.addsitedir(pth_file.base_dir, set())
-            unittest.FunctionTestCase(pth_file.test)
+            self.pth_file_tests(pth_file)
         finally:
             pth_file.cleanup()
 
@@ -92,7 +100,7 @@ class PthFile(object):
         self.filename = filename_base + ".pth"
         self.base_dir = os.path.abspath('')
         self.file_path = os.path.join(self.base_dir, self.filename)
-        self.imported = "time"
+        self.imported = imported
         self.good_dirname = good_dirname
         self.bad_dirname = bad_dirname
         self.good_dir_path = os.path.join(self.base_dir, self.good_dirname)
@@ -120,34 +128,23 @@ class PthFile(object):
             FILE.close()
         os.mkdir(self.good_dir_path)
 
-    def cleanup(self):
+    def cleanup(self, prep=False):
         """Make sure that the .pth file is deleted, self.imported is not in
         sys.modules, and that both self.good_dirname and self.bad_dirname are
         not existing directories."""
-        try:
+        if os.path.exists(self.file_path):
             os.remove(self.file_path)
-        except OSError:
-            pass
-        try:
-            del sys.modules[self.imported]
-        except KeyError:
-            pass
-        try:
+        if prep:
+            self.imported_module = sys.modules.get(self.imported)
+            if self.imported_module:
+                del sys.modules[self.imported]
+        else:
+            if self.imported_module:
+                sys.modules[self.imported] = self.imported_module
+        if os.path.exists(self.good_dir_path):
             os.rmdir(self.good_dir_path)
-        except OSError:
-            pass
-        try:
+        if os.path.exists(self.bad_dir_path):
             os.rmdir(self.bad_dir_path)
-        except OSError:
-            pass
-
-    def test(self):
-        """Test to make sure that was and was not supposed to be created by
-        using the .pth file occurred"""
-        assert site.makepath(self.good_dir_path)[0] in sys.path
-        assert self.imported in sys.modules
-        assert not os.path.exists(self.bad_dir_path)
-
 
 class ImportSideEffectTests(unittest.TestCase):
     """Test side-effects from importing 'site'."""