memdb conflict check, thanks Luca

VERSION

@@ -1 +1 @@
-Version 2.7.4-stable+timestamp.2013.11.13.14.06.31
+Version 2.7.4-stable+timestamp.2013.11.14.13.28.53

gluon/contrib/memdb.py

@@ -253,12 +253,15 @@ class Table(DALStorage):
 
         self._db(self.id > 0).delete()
 
-    def insert(self, **fields):
-        id = self._create_id()
-        if self.update(id, **fields):
-            return long(id)
+
+    def insert(self, **fields): 
+        # Checks 3 times that the id is new. 3 times is enough! 
+        for i in range(3): 
+            id = self._create_id() 
+            if self.get(id) is None and self.update(id, **fields): 
+                return long(id) 
         else:
-            return None
+            raise RuntimeError("Too many ID conflicts")
 
     def get(self, id):
         val = self._tableobj.get(self._id_to_key(id))