Mysterious Langchain Azure OpenAI Problems

I was banging my head on this problem for hours. Using langchain and our Azure OpenAI model, I kept getting a Value error:

As of openai>=1.0.0, Azure endpoints should be specified via the
`azure_endpoint` param not `openai_api_base` (or alias `base_url`).

I was not defining openai_api_base anywhere in my code. LLMs were no use but I did find the suggestion on Reddit to check if openai_api_base was an environment variable.

Sure enough, I had defined that months ago, never used it, and forgot it. Deleted the variable and problem solved.

Check the basics!