For srctree tests, include the test directory in the PYTHONPATH of...

For srctree tests, include the test directory in the PYTHONPATH of subprocesses, but not in the own sys.path of the test runner.

runtests.py

@@ -1738,8 +1738,6 @@ class EndToEndTest(unittest.TestCase):
         _, self.commands = unpack_source_tree(self.treefile, self.workdir, self.cython_root)
         self.old_dir = os.getcwd()
         os.chdir(self.workdir)
-        if self.workdir not in sys.path:
-            sys.path.insert(0, self.workdir)
 
     def tearDown(self):
         if self.cleanup_workdir:
@@ -1764,7 +1762,7 @@ class EndToEndTest(unittest.TestCase):
         env = dict(os.environ)
         new_path = self.cython_syspath
         if old_path:
-            new_path = new_path + os.pathsep + old_path
+            new_path = new_path + os.pathsep + self.workdir + os.pathsep + old_path
         env['PYTHONPATH'] = new_path
         if not env.get("PYTHONIOENCODING"):
             env["PYTHONIOENCODING"] = sys.stdout.encoding or sys.getdefaultencoding()