Fix _delete_row() so it actually works!

Change-Id: Ieec0348d750d4996118245fe34e09c09c221f0a5
diff --git a/db/db.py b/db/db.py
index 28921d2..014d7de 100644
--- a/db/db.py
+++ b/db/db.py
@@ -130,8 +130,8 @@
 
     def _delete_row(self, table, field, value):
         try:
-            sql = "DELETE FROM %s WHERE %s = %s"
-            data = (table, field, value)
+            sql = "DELETE FROM %s WHERE %s = %s" % (table, field, '%s')
+            data = (value,)
             self.cursor.execute(sql, data)
             self.connection.commit()
         except: