Add message parameter to PDB.savepoint for better logging.

Helps to have a visual on which methods are creating the saves.

etiquette/decorators.py

@@ -78,7 +78,7 @@ def transaction(method):
     @functools.wraps(method)
     def wrapped_transaction(self, *args, **kwargs):
         photodb = _get_relevant_photodb(self)
-        savepoint_id = photodb.savepoint()
+        savepoint_id = photodb.savepoint(message=method.__qualname__)
         try:
             result = method(self, *args, **kwargs)
         except Exception as e:

etiquette/photodb.py

@@ -720,8 +720,11 @@ class PDBSQLMixin:
             if item == restore_to:
                 break
 
-    def savepoint(self):
+    def savepoint(self, message=None):
         savepoint_id = helpers.random_hex(length=16)
+        if message:
+            self.log.debug('Savepoint %s for %s.', savepoint_id, message)
+        else:
             self.log.debug('Savepoint %s.', savepoint_id)
         query = 'SAVEPOINT "%s"' % savepoint_id
         self.sql.execute(query)