Karthikeyan, my apologies for the slow reply -- I posted this right before I went to bed.


To emphasize, the change to the formatting of the string contents, by adding the filename, I think is not problematic: I'm using ellipses to elide everything before and after my custom "warning" message.

Rather, I think the problem is that the string is being rendered as a '' string, instead of as a "" string; IOW:

'Test string with \'enclosing\' single quotes'

vs

"Test string with 'enclosing' double quotes"

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In the interim, as you suggest, Karthikeyan, I can just conditionally skip the doctests on 3.8 with a suitable pytest -k flag.