test-lock.py: copy-edit assertions about file existing

Before: expected lock to exists but actually did not exists
After:  expected lock to exist but actually did not exist

tests/test-lock.py

@@ -80,9 +80,9 b' class teststate(object):'
 
     def _toexists(self, exists):
         if exists:
-            return 'exists'
+            return 'exist'
         else:
-            return 'not exists'
+            return 'not exist'
 
 class testlock(unittest.TestCase):
     def testlock(self):