bpo-33358: Fix test_embed.test_pre_initialization_sys_options (GH-6612)

Fix test_embed.test_pre_initialization_sys_options() when building with --enable-shared
(cherry picked from commit 4114846)

Co-authored-by: Pablo Galindo <Pablogsal@gmail.com>

Author: miss-islington

Lib/test/test_embed.py

@@ -208,7 +208,7 @@ def test_pre_initialization_sys_options(self):
         Checks that sys.warnoptions and sys._xoptions can be set before the
         runtime is initialized (otherwise they won't be effective).
         """
-        env = dict(PYTHONPATH=os.pathsep.join(sys.path))
+        env = dict(os.environ, PYTHONPATH=os.pathsep.join(sys.path))
         out, err = self.run_embedded_interpreter(
                         "pre_initialization_sys_options", env=env)
         expected_output = (

Misc/NEWS.d/next/Tests/2018-04-27-11-46-35.bpo-33358._OcR59.rst

@@ -0,0 +1,2 @@
+Fix ``test_embed.test_pre_initialization_sys_options()`` when the interpreter
+is built with ``--enable-shared``.