Merge pull request pallets#858 from svieira/patch-2

Patch for tutorial (minor code error)

Author: Daniel Neuhäuser

docs/tutorial/dbinit.rst

@@ -25,7 +25,7 @@ database.  Let me show you the code first.  Just add that function below
 the `connect_db` function in `flaskr.py`::
 
     def init_db():
-        app app.app_context():
+        with app.app_context():
             db = get_db()
             with app.open_resource('schema.sql', mode='r') as f:
                 db.cursor().executescript(f.read())