in clear() clear journals and node files.

AFAICT clear() is never called by current codebase, but this fixes a
flake8 issue where the loop variable (renamed to data_type) was unused
within loop. Also this triggerd a look at Database.clear() in
rdbms_common.py which was not clearing the journals.

Author: rouilj

roundup/backends/back_anydbm.py

@@ -239,8 +239,8 @@ def clear(self):
         """
         logging.getLogger('roundup.hyperdb.backend').info('clear')
         for cn in self.classes:
-            for dummy in 'nodes', 'journals':
-                path = os.path.join(self.dir, 'journals.%s' % cn)
+            for data_type in 'nodes', 'journals':
+                path = os.path.join(self.dir, '%s.%s' % (data_type, cn))
                 if os.path.exists(path):
                     os.remove(path)
                 elif os.path.exists(path+'.db'):    # dbm appends .db