test_custom_tokenizer_bug.py loaded Xenova/llama-3-tokenizer from
HuggingFace Hub at test time, so it flaked on shared CI runners whenever
HF returned 429 Too Many Requests; the surfaced LocalEntryNotFoundError
made it look like a connectivity bug.
Rewrite the suite to mock the one network boundary
(litellm.utils.Tokenizer.from_pretrained) while running the proxy's real
extraction-and-selection path. The regression test now asserts the
configured identifier from model_info.custom_tokenizer actually reaches
from_pretrained and that the response reports the huggingface tokenizer,
which the previous llama-3-named test could not distinguish from the
default path. A control test pins the no-custom-tokenizer case to the
OpenAI tokenizer with from_pretrained asserted unused.
Verified by reintroducing the original bug (model_info left unpopulated
from the deployment): the regression test fails (from_pretrained called 0
times) while the control stays green.
