[IMPR] clean up time.py

- remove unused variable ZERO
- fix type hint

Change-Id: I8a3b64a1188af57949ea9305305efe85f7e58215
---
M pywikibot/time.py
1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/pywikibot/time.py b/pywikibot/time.py
index f3a6d46..0e14332 100644
--- a/pywikibot/time.py
+++ b/pywikibot/time.py
@@ -34,8 +34,6 @@
     # 'months' and 'minutes' were removed because confusion outweighs merit
 })
 
-ZERO = datetime.timedelta(0)
-
 
 class Timestamp(datetime.datetime):
 
@@ -211,7 +209,7 @@
         msg = "time data '{timestr}' does not match any format."
         raise ValueError(msg.format(timestr=timestr))
 
-    def clone(self) -> datetime.datetime:
+    def clone(self) -> 'Timestamp':
         """Clone this instance."""
         return self.replace(microsecond=self.microsecond)
 

