Extracting a list of values from column A where column B contains a specific value

From the following table:

ID     Status
001    Done
002    Done
003    Done
004    Error
005    Done
006    Error
007    Done
008    Done
009    Error

I want to extract a list/string of all the IDs with an 'Error'. In other words, a cell which looks like this:

004, 006, 009

Thanks in advance.

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