make sure the parser flags and passed onto the compiler

This fixes "from __future__ import unicode_literals" in an exec statment
See #4225
diff --git a/Lib/test/test_future.py b/Lib/test/test_future.py
index 1432e74..81d0a3e 100644
--- a/Lib/test/test_future.py
+++ b/Lib/test/test_future.py
@@ -106,6 +106,11 @@
         test_support.unload("test.test_future5")
         from test import test_future5
 
+    def test_unicode_literals_exec(self):
+        scope = {}
+        exec "from __future__ import unicode_literals; x = ''" in scope
+        self.assertTrue(isinstance(scope["x"], unicode))
+
 
 def test_main():
     test_support.run_unittest(FutureTest)