[iap] Debug why iap test doesn't pass locally.

[tmatsuo]

If you run iap/iap_test.py locally, it fails with the following logs:
I'm not sure why. Maybe there're some firewall rules on the project?
I don't have access to the project gcp-devrel-iap-reflect right now, so it's hard to debug further. I'm trying to obtain the ownership of that project.

iap_test.py::test_main FAILED                                                                                                                               [100%]

============================================================================ FAILURES =============================================================================
____________________________________________________________________________ test_main ____________________________________________________________________________
Traceback (most recent call last):
  File "/usr/local/google/home/tmatsuo/work/python-docs-samples/iap/iap_test.py", line 51, in test_main
    IAP_CLIENT_ID)
  File "/usr/local/google/home/tmatsuo/work/python-docs-samples/iap/make_iap_request.py", line 54, in make_iap_request
    raise Exception('Service account does not have permission to '
Exception: Service account does not have permission to access the IAP-protected application.
--------------------------------- generated xml file: /usr/local/google/home/tmatsuo/work/python-docs-samples/iap/sponge_log.xml ----------------------------------
===Flaky Test Report===

test_main failed (1 runs remaining out of 2).
        <class 'Exception'>
        Service account does not have permission to access the IAP-protected application.
        [<TracebackEntry /usr/local/google/home/tmatsuo/work/python-docs-samples/iap/iap_test.py:51>, <TracebackEntry /usr/local/google/home/tmatsuo/work/python-docs-samples/iap/make_iap_request.py:54>]
test_main failed; it passed 0 out of the required 1 times.
        <class 'Exception'>
        Service account does not have permission to access the IAP-protected application.
        [<TracebackEntry /usr/local/google/home/tmatsuo/work/python-docs-samples/iap/iap_test.py:51>, <TracebackEntry /usr/local/google/home/tmatsuo/work/python-docs-samples/iap/make_iap_request.py:54>]

===End Flaky Test Report===
======================================================================== 1 failed in 0.60s ========================================================================
nox > Command pytest --junitxml=sponge_log.xml failed with exit code 1
nox > Session py-3.7 failed.

[tmatsuo]

I just realized that the test succeeds on my workstation, closing.