Catch server errors and return alert to the user about auto-evaluator

[rlancemartin]

Confirm now we will see a server error:

Error
There was an error from the server.

[rlancemartin]

But, the railway deployed API actually will just return None.

This throws a server error:

If you want this text to be encoded as a special token, pass it to `allowed_special`, e.g. `allowed_special={'<|endofprompt|>', ...}`.
ValueError: Encountered text corresponding to disallowed special token '<|endofprompt|>'.
If you want this text to be encoded as a special token, pass it to `allowed_special`, e.g. `allowed_special={'<|endofprompt|>', ...}`.
If you want this text to be encoded as normal text, disable the check for this token by passing `disallowed_special=(enc.special_tokens_set - {'<|endofprompt|>'})`.
To disable this check for all special tokens, pass `disallowed_special=()`.
If you want this text to be encoded as normal text, disable the check for this token by passing `disallowed_special=(enc.special_tokens_set - {'<|endofprompt|>'})`.
To disable this check for all special tokens, pass `disallowed_special=()`.

But the API returns None:

curl -X POST -F "files=@docs/transformers/2303.08774.pdf" -F "num_eval_questions=1" -F "chunk_chars=1000" -F "overlap=100" -F "split_method=RecursiveTextSplitter" -F "retriever_type=similarity-search" -F "embeddings=OpenAI" -F "model_version=gpt-3.5-turbo" -F "grade_prompt=Fast" -F "num_neighbors=3" https://auto-evaluator-production.up.railway.app/evaluator-stream

So, in prod we could catch None from the server and just alert an error.