Fixed typo in SQLALCHEMY_DATABASE_URI

instance/config.py.default

@@ -3,4 +3,4 @@ DB_USER = 'your_database_username'
 DB_PW = 'your_database_password'
 DB_HOST = 'localhost'
 DB_NAME = 'your_database_name'
-SQLALCHEMY_DATABASE_URI= 'mysql://{user}:{pw}@{url}/{db}'.format(user=DB_USER,pw=DB_PW,url=DB_URL,db=DB_NAME)
+SQLALCHEMY_DATABASE_URI= 'mysql://{user}:{pw}@{host}/{db}'.format(user=DB_USER,pw=DB_PW,host=DB_HOST,db=DB_NAME)