[Flaky test] `lms/djangoapps/email_marketing/tests/test_signals.py::SailthruTests::test_update_course_enrollment`

This test fails intermittently and has been deleted according to the Flaky Test Process in https://github.com/openedx/edx-platform/pull/23075

See docs on how to address flaky tests for why this should be fixed and how to go about it.

• Build where the test failed: https://build.testeng.edx.org/job/edx-platform-python-pipeline-pr/14380/
• Build where the test passed: https://build.testeng.edx.org/job/edx-platform-python-pipeline-pr/14387/

Failure output:

Run Tests / lms-unit / lms.djangoapps.email_marketing.tests.test_signals.SailthruTests.test_update_course_enrollment (from pytest)

Failing for the past 1 build (Since Failed#14380 )
Took 25 ms.
Error Message
AssertionError: expected call not found. Expected: purchase('test@edx.org', [{'id': 'edX/toy/2012_Fall-audit', 'url': 'http://lms.testserver.fake/courses/edX/toy/2012_Fall/info', 'price': 0, 'vars': {'course_run_id': 'edX/toy/2012_Fall', 'mode': 'audit'}, 'title': 'Course edX/toy/2012_Fall mode: audit', 'qty': 1}], options={}) Actual: purchase('test@edx.org', [{'id': 'edX/toy/2012_Fall-audit', 'url': 'http://lms.testserver.fake/courses/edX/toy/2012_Fall/info', 'price': 0, 'vars': {'course_run_id': 'edX/toy/2012_Fall', 'mode': 'audit'}, 'title': 'Course edX/toy/2012_Fall mode: audit', 'qty': 1}], options={'send_template': 'enroll_template'})
Stacktrace
self = <test_signals.SailthruTests testMethod=test_update_course_enrollment>
mock_sailthru_api_post = <MagicMock name='api_post' id='140687767418192'>
mock_sailthru_api_get = <MagicMock name='api_get' id='140687827763384'>
mock_sailthru_purchase = <MagicMock name='purchase' id='140687763071160'>

    @patch('sailthru.sailthru_client.SailthruClient.purchase')
    @patch('sailthru.sailthru_client.SailthruClient.api_get')
    @patch('sailthru.sailthru_client.SailthruClient.api_post')
    def test_update_course_enrollment(self, mock_sailthru_api_post,
                                      mock_sailthru_api_get, mock_sailthru_purchase):
        """test update sailthru user record"""
    
        # create mocked Sailthru API responses
        mock_sailthru_api_post.return_value = MockSailthruResponse({'ok': True})
        mock_sailthru_api_get.return_value = MockSailthruResponse({'user': {"id": TEST_EMAIL, "fields": {"vars": 1}}})
        mock_sailthru_purchase.return_value = MockSailthruResponse({'ok': True})
        self.user.email = TEST_EMAIL
        CourseEnrollmentFactory(user=self.user, course_id=self.course_id)
        with patch('email_marketing.tasks.build_course_url') as m:
            m.return_value = self.course_url
            update_course_enrollment(TEST_EMAIL, self.course_id, 'audit')
        item = [{
            'vars': {'course_run_id': u'edX/toy/2012_Fall', 'mode': 'audit'},
            'url': self.course_url,
            'price': 0,
            'qty': 1,
            'id': 'edX/toy/2012_Fall-audit',
            'title': 'Course edX/toy/2012_Fall mode: audit'
        }]
>       mock_sailthru_purchase.assert_called_with(TEST_EMAIL, item, options={})

lms/djangoapps/email_marketing/tests/test_signals.py:644: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 
../edx-venv-3.5/edx-venv/lib/python3.5/site-packages/mock/mock.py:944: in assert_called_with
    six.raise_from(AssertionError(_error_message(cause)), cause)
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 

value = None, from_value = None

>   ???
E   AssertionError: expected call not found.
E   Expected: purchase('test@edx.org', [{'id': 'edX/toy/2012_Fall-audit', 'url': 'http://lms.testserver.fake/courses/edX/toy/2012_Fall/info', 'price': 0, 'vars': {'course_run_id': 'edX/toy/2012_Fall', 'mode': 'audit'}, 'title': 'Course edX/toy/2012_Fall mode: audit', 'qty': 1}], options={})
E   Actual: purchase('test@edx.org', [{'id': 'edX/toy/2012_Fall-audit', 'url': 'http://lms.testserver.fake/courses/edX/toy/2012_Fall/info', 'price': 0, 'vars': {'course_run_id': 'edX/toy/2012_Fall', 'mode': 'audit'}, 'title': 'Course edX/toy/2012_Fall mode: audit', 'qty': 1}], options={'send_template': 'enroll_template'})

<string>:3: AssertionError

Migrated from private ticket https://2u-internal.atlassian.net/issues/CR-1806

Start with lms/djangoapps/email_marketing/tests/test_signals.py::SailthruTests::test_update_course_enrollment and compare the failing and passing builds linked in the issue. Read the flaky-test process and the email marketing enrollment path to determine why the mocked purchase options differ; done means the test is restored or its replacement reliably verifies the intended call.