Add test cases

Author: neonene

Lib/test/datetimetester.py

@@ -7367,6 +7367,40 @@ def gen():
             res = self.assert_python_in_subinterp(True, script, setup='')
             self.assertFalse(res.err)
 
+        script = textwrap.dedent("""
+            import gc
+            import sys
+            import _testcapi
+
+            def emulate_interp_restart():
+                del sys.modules['_datetime']
+                try:
+                    del sys.modules['datetime']
+                except KeyError:
+                    pass
+                gc.collect()  # unload
+
+            _testcapi.test_datetime_capi()  # only once
+            timedelta = _testcapi.get_capi_types()['timedelta']
+            emulate_interp_restart()
+            timedelta(days=1)
+            emulate_interp_restart()
+
+            def gen():
+                try:
+                    yield
+                finally:
+                    # Exceptions are ignored here
+                    assert not sys.modules
+                    timedelta(days=1)
+
+            it = gen()
+            next(it)
+            """)
+        with self.subTest('MainInterpreter Restart'):
+            res = script_helper.assert_python_ok('-c', script)
+            self.assertIn(b'ImportError: sys.meta_path is None', res.err)
+
         script = textwrap.dedent("""
             import sys
             timedelta = _testcapi.get_capi_types()['timedelta']