How to use the safety.errors.DatabaseFileNotFoundError function in safety

db=db, 
                               key=key)

        if output:
            with open(output, 'w+') as output_file:
                output_file.write(output_report)
        else:
            click.secho(output_report, nl=False if bare and not vulns else True)
        sys.exit(-1 if vulns else 0)
    except InvalidKeyError:
        click.secho("Your API Key '{key}' is invalid. See {link}".format(
            key=key, link='https://goo.gl/O7Y1rS'),
            fg="red",
            file=sys.stderr)
        sys.exit(-1)
    except DatabaseFileNotFoundError:
        click.secho("Unable to load vulnerability database from {db}".format(db=db), fg="red", file=sys.stderr)
        sys.exit(-1)
    except DatabaseFetchError:
        click.secho("Unable to load vulnerability database", fg="red", file=sys.stderr)
        sys.exit(-1)

db=db, 
                               key=key)

        if output:
            with open(output, 'w+') as output_file:
                output_file.write(output_report)
        else:
            click.secho(output_report, nl=False if bare and not vulns else True)
        sys.exit(-1 if vulns else 0)
    except InvalidKeyError:
        click.secho("Your API Key '{key}' is invalid. See {link}".format(
            key=key, link='https://goo.gl/O7Y1rS'),
            fg="red",
            file=sys.stderr)
        sys.exit(-1)
    except DatabaseFileNotFoundError:
        click.secho("Unable to load vulnerability database from {db}".format(db=db), fg="red", file=sys.stderr)
        sys.exit(-1)
    except DatabaseFetchError:
        click.secho("Unable to load vulnerability database", fg="red", file=sys.stderr)
        sys.exit(-1)

def fetch_database_file(path, db_name):
    full_path = os.path.join(path, db_name)
    if not os.path.exists(full_path):
        raise DatabaseFileNotFoundError()
    with open(full_path) as f:
        return json.loads(f.read())