Fix test_decimal and test_xml_etree.

Author: serhiy-storchaka

Lib/test/test_decimal.py

@@ -62,7 +62,7 @@
 
 C = import_fresh_module('decimal', fresh=['_decimal'])
 P = import_fresh_module('decimal', blocked=['_decimal'])
-orig_sys_decimal = sys.modules['decimal']
+import decimal as orig_sys_decimal
 
 # fractions module must import the correct decimal module.
 cfractions = import_fresh_module('fractions', fresh=['fractions'])

Lib/test/test_xml_etree.py

@@ -26,7 +26,7 @@
 from test import support
 from test.support import os_helper
 from test.support import warnings_helper
-from test.support import findfile, gc_collect, swap_attr
+from test.support import findfile, gc_collect, swap_attr, swap_item
 from test.support.import_helper import import_fresh_module
 from test.support.os_helper import TESTFN
 
@@ -167,21 +167,18 @@ def setUpClass(cls):
         cls.modules = {pyET, ET}
 
     def pickleRoundTrip(self, obj, name, dumper, loader, proto):
-        save_m = sys.modules[name]
         try:
-            sys.modules[name] = dumper
-            temp = pickle.dumps(obj, proto)
-            sys.modules[name] = loader
-            result = pickle.loads(temp)
+            with swap_item(sys.modules, name, dumper):
+                temp = pickle.dumps(obj, proto)
+            with swap_item(sys.modules, name, loader):
+                result = pickle.loads(temp)
         except pickle.PicklingError as pe:
             # pyET must be second, because pyET may be (equal to) ET.
             human = dict([(ET, "cET"), (pyET, "pyET")])
             raise support.TestFailed("Failed to round-trip %r from %r to %r"
                                      % (obj,
                                         human.get(dumper, dumper),
                                         human.get(loader, loader))) from pe
-        finally:
-            sys.modules[name] = save_m
         return result
 
     def assertEqualElements(self, alice, bob):