The root cause was load_installed_languages() of argostranslate
being called at the top of the file instead of inside a function,
this caused the list of installed languages to incorrectly be
returned as an empty list.

- Remove unnecessary import
- Reorder imports
- Fix whitespace issues

When an API key is passed, fail in the case of an invalid API key even
if an API key is not required. This allows the user to know that the API
key is invalid. Otherwise, they work under the assumption that the API
key is correct, even though it is not.

This is useful for applications that want to know beforehand if usage of
an API key is supported.

Also removes limiter exemption

This is useful for applications that want to know beforehand if an API
key is necessary before accessing the running instance.