The default TestCase.__call__ collects errors in a test result that
was never retrieved, so errors were silently ignored.

By using TestCase.debug , we let errors propagate.

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Minimal reproduction is running directly (ie. not with python -m unittest)
a script like this:

    import unittest

    class T(unittest.TestCase):
      def method(self):
        print('ah ?')
        boom
        print('oh')

    t = T("method")
    t()  # no error
    t.debug()  # NameError: name 'boom' is not defined