User exceptions are ignored if data is frozen

[jakkdl]

def test_frozen_things():
    # Hypothesis reraises the TypeError as a StopTest, because the data is Frozen.
    @given(st.data())
    def foo(data):
        data.conjecture_data.freeze()
        raise TypeError("oops")

    foo()

It should be possible to repro without manually freezing the data as well, especially if invoking async stuff.

Offending lines:

hypothesis/hypothesis-python/src/hypothesis/core.py

Lines 1077 to 1089 in 0991e76

	except failure_exceptions_to_catch() as e:
	# If an unhandled (i.e., non-Hypothesis) error was raised by
	# Hypothesis-internal code, re-raise it as a fatal error instead
	# of treating it as a test failure.
	filepath = traceback.extract_tb(e.__traceback__)[-1][0]
	if is_hypothesis_file(filepath) and not isinstance(e, HypothesisException):
	raise
	if data.frozen:
	# This can happen if an error occurred in a finally
	# block somewhere, suppressing our original StopTest.
	# We raise a new one here to resume normal operation.
	raise StopTest(data.testcounter) from e

Possible fixes:

1. reraise the exception saved in StopTest.__cause__ when the StopTest is handled. I'm getting ~8 hits for except StopTest in non-test code though, so could get messy.
   • might be better to save the exception in the DataObject
2. Traverse e.__context__ to see if we actually did raise Stoptest before handling. Although this would still suppress user errors in teardown if we did raise Stoptest, so it's only a partial fix. (edit: except the test_error_is_in_finally test works.. so maybe this would fix it???)

Git blame shows ac0d02a as adding the logic. Though I don't understand the code intimately enough to see what the difference between their added test, which ultimately reraises their ValueError, and mine is.

See discussion in #4110 (comment)