Hunt for root cause of flaky test in Python

There is a flaky test, and we have no clue what the root cause could be.

with pytest.raises(foo.geocoder.GeocodingFailed):
    foo.geocoder.geocode('not a valid place')

Sometimes the exception does not happen.

I looked at the docs how to handle failures, but this did not help.

How to trace geocode() so that if the exception does not happen, I see a trace?

I looked at the trace module of the standard library. But there seems to be no easy way to get the trace as string.

With "a trace" I mean: A trace of all lines which got executed during gecode(). I would like to see method calls and returns statements with indentation. I want to ignore lines from the Python standard library.

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