Issue #9527: datetime.astimezone() method will now supply a class
timezone instance corresponding to the system local timezone when
called with no arguments.
diff --git a/Lib/datetime.py b/Lib/datetime.py
index ce88d85..e4d7161 100644
--- a/Lib/datetime.py
+++ b/Lib/datetime.py
@@ -1501,7 +1501,7 @@
             localtm = _time.localtime(ts)
             local = datetime(*localtm[:6])
             try:
-                # Extract TZ data if available 
+                # Extract TZ data if available
                 gmtoff = localtm.tm_gmtoff
                 zone = localtm.tm_zone
             except AttributeError:
@@ -1517,7 +1517,7 @@
                     tz = timezone(delta)
             else:
                 tz = timezone(timedelta(seconds=-gmtoff), zone)
-                
+
         elif not isinstance(tz, tzinfo):
             raise TypeError("tz argument must be an instance of tzinfo")
 
diff --git a/Lib/test/datetimetester.py b/Lib/test/datetimetester.py
index e045447..4181d4f 100644
--- a/Lib/test/datetimetester.py
+++ b/Lib/test/datetimetester.py
@@ -3283,11 +3283,11 @@
         dt = self.theclass(2012, 11, 4, 6, 30, tzinfo=timezone.utc)
         local = dt.astimezone()
         self.assertEqual(dt, local)
-        self.assertEqual(local.strftime("%z %Z"), "+0500 EST") 
+        self.assertEqual(local.strftime("%z %Z"), "+0500 EST")
         dt = self.theclass(2012, 11, 4, 5, 30, tzinfo=timezone.utc)
         local = dt.astimezone()
         self.assertEqual(dt, local)
-        self.assertEqual(local.strftime("%z %Z"), "+0400 EDT") 
+        self.assertEqual(local.strftime("%z %Z"), "+0400 EDT")
 
     def test_aware_subtract(self):
         cls = self.theclass