@rbcollins that is exactly what was trying to say in previous comment. We can make a change to current patch that won't affect behavior. In old API in this sequence of filters last filter was never used:

simplefilter("ignore")
simplefilter("error", append=True)
simplefilter("ignore", append=True)  # never used

So I suggest that new patch should work like this:


simplefilter("error")
simplefilter("ignore", append=True)  # appends new filter to the end

simplefilter("ignore")
simplefilter("error", append=True)
simplefilter("ignore", append=True)  # does nothing since same filter is present.

This way filtering will work in the same way it worked before patch and we won't have duplicates.

I'll update the patch as soon as I will get to my computer.