[Fixed]-Variable not found. Declare it as envvar or define a default value

Change the name of the file: my_app.env must be .env.

From the source code:

class AutoConfig(object):
    """
    Autodetects the config file and type.
    """
    SUPPORTED = {
        'settings.ini': RepositoryIni,
        '.env': RepositoryEnv,
    }