tests: remove extra empty lines

qubesadmin/tests/__init__.py

@@ -107,11 +107,9 @@ class _AssertNotRaisesContext(object):
 
         self.failureException = test_case.failureException
 
-
     def __enter__(self):
         return self
 
-
     def __exit__(self, exc_type, exc_value, tb):
         if exc_type is None:
             return True