AttributeError when using --slowreportpath with Django 3.1

[haplo]

I have added django-slow-tests to a Django 3.1-based project. --slowreport works fine, but --slowreportpath is failing with this stacktrace:

$ ./manage.py test --slowreport --slowreportpath=report.json
Creating test database for alias 'default'...
System check identified no issues (0 silenced).
...........................................................................
----------------------------------------------------------------------
Ran 75 tests in 8.603s

OK
Destroying test database for alias 'default'...
Traceback (most recent call last):
  File "./manage.py", line 26, in <module>
    execute_from_command_line(sys.argv)
  File "/home/fidel/Code/solidshape/backend/platform/.venv/lib/python3.8/site-packages/django/core/management/__init__.py", line 401, in execute_from_command_line
    utility.execute()
  File "/home/fidel/Code/solidshape/backend/platform/.venv/lib/python3.8/site-packages/django/core/management/__init__.py", line 395, in execute
    self.fetch_command(subcommand).run_from_argv(self.argv)
  File "/home/fidel/Code/solidshape/backend/platform/.venv/lib/python3.8/site-packages/django/core/management/commands/test.py", line 23, in run_from_argv
    super().run_from_argv(argv)
  File "/home/fidel/Code/solidshape/backend/platform/.venv/lib/python3.8/site-packages/django/core/management/base.py", line 330, in run_from_argv
    self.execute(*args, **cmd_options)
  File "/home/fidel/Code/solidshape/backend/platform/.venv/lib/python3.8/site-packages/django/core/management/base.py", line 371, in execute
    output = self.handle(*args, **options)
  File "/home/fidel/Code/solidshape/backend/platform/.venv/lib/python3.8/site-packages/django/core/management/commands/test.py", line 53, in handle
    failures = test_runner.run_tests(test_labels)
  File "/home/fidel/Code/solidshape/backend/platform/.venv/lib/python3.8/site-packages/django/test/runner.py", line 712, in run_tests
    return self.suite_result(suite, result)
  File "/home/fidel/Code/solidshape/backend/platform/.venv/lib/python3.8/site-packages/django_slowtests/testrunner.py", line 260, in suite_result
    self.generate_report(test_results, result)
  File "/home/fidel/Code/solidshape/backend/platform/.venv/lib/python3.8/site-packages/django_slowtests/testrunner.py", line 178, in generate_report
    'nb_tests': result.testsRun,
AttributeError: 'tuple' object has no attribute 'testsRun'

[m-kc]

I'm having the same issue on Django 2.2 + Python 3.7, stack trace appears to be identical aside from line numbers:

Traceback (most recent call last):
  File "./manage.py", line 9, in <module>
    execute_from_command_line(sys.argv)
  File "{{...}}/lib/python3.7/site-packages/django/core/management/__init__.py", line 381, in execute_from_command_line
    utility.execute()
  File "{{...}}/lib/python3.7/site-packages/django/core/management/__init__.py", line 375, in execute
    self.fetch_command(subcommand).run_from_argv(self.argv)
  File "{{...}}/lib/python3.7/site-packages/django/core/management/commands/test.py", line 23, in run_from_argv
    super().run_from_argv(argv)
  File "{{...}}/lib/python3.7/site-packages/django/core/management/base.py", line 323, in run_from_argv
    self.execute(*args, **cmd_options)
  File "{{...}}/lib/python3.7/site-packages/django/core/management/base.py", line 364, in execute
    output = self.handle(*args, **options)
  File "{{...}}/lib/python3.7/site-packages/test_without_migrations/management/commands/_base.py", line 78, in handle
    super(CommandMixin, self).handle(*test_labels, **options)
  File "{{...}}/lib/python3.7/site-packages/django/core/management/commands/test.py", line 53, in handle
    failures = test_runner.run_tests(test_labels)
  File "{{...}}/lib/python3.7/site-packages/django/test/runner.py", line 646, in run_tests
    return self.suite_result(suite, result)
  File "{{...}}/lib/python3.7/site-packages/django_slowtests/testrunner.py", line 260, in suite_result
    self.generate_report(test_results, result)
  File "{{...}}/lib/python3.7/site-packages/django_slowtests/testrunner.py", line 178, in generate_report
    'nb_tests': result.testsRun,
AttributeError: 'tuple' object has no attribute 'testsRun'