sqlalchemy.exc.ArgumentError: Could not parse rfc1738 URL from string

You are not using a valid URL in the connection string.

Review the documentation on how the MySQL connection URLs need to be structured: http://docs.sqlalchemy.org/en/latest/dialects/mysql.html.

Depending on the MySQL driver that you use the connection URL is different. For example, if you use pymysql, your URL should be:

mysql+pymysql://<username>:<password>@<host>/<dbname>[?<options>]