New 'page_size' argument breaks unit tests under Python 3.6

[tseaver]

PR #520 added passing page_size to the google.api_core.page_iterator.HTTPIterator constructor, which is a feature added only in google-api-core 1.29.0. testing/constraints-3.6.txt pins google-cloud-core==1.6.0, the minimum version specified in setup.py, but does not pin google-api-core, which results in:

$ git remote -v
origin	git@github.com:googleapis/python-storage (fetch)
origin	git@github.com:googleapis/python-storage (push)

$ git status
On branch master
Your branch is up to date with 'origin/master'.

nothing to commit, working tree clean

$ git log -1
commit 4abb40310eca7ec45afc4bc5e4dfafbe083e74d2 (HEAD -> master, origin/master, origin/HEAD)
Author: Tres Seaver <tseaver@palladion.com>
Date:   Tue Jul 27 13:43:42 2021 -0400

    fix: make 'requests.exceptions.ChunkedEncodingError retryable by default (#526)
    
    Closes #525.

$ .nox/unit-3-6/bin/pip list | grep google
google-api-core          1.27.0
google-auth              1.24.0
google-cloud-core        1.6.0
google-cloud-storage     1.41.1   /path/to/python-storage
google-crc32c            1.1.2
google-resumable-media   1.3.0
googleapis-common-protos 1.53.0

$ nox -re unit-3.6
nox > Running session unit-3.6
nox > Creating virtual environment (virtualenv) using python3.6 in .nox/unit-3-6
nox > python -m pip install mock pytest pytest-cov -c /home/tseaver/projects/agendaless/Google/src/python-storage/testing/constraints-3.6.txt
nox > python -m pip install -e . -c /home/tseaver/projects/agendaless/Google/src/python-storage/testing/constraints-3.6.txt
nox > py.test --quiet --cov=google.cloud.storage --cov=google.cloud --cov=tests.unit --cov-append --cov-config=.coveragerc --cov-report= --cov-fail-under=0 tests/unit
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.........................FF............................................. [ 83%]
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.....................                                                    [100%]Coverage.py warning: Module google.cloud was previously imported, but not measured (module-not-measured)

=================================== FAILURES ===================================
__________________ TestClient.test__list_resource_w_defaults ___________________

self = <tests.unit.test_client.TestClient testMethod=test__list_resource_w_defaults>

    def test__list_resource_w_defaults(self):
        import functools
        from google.api_core.page_iterator import HTTPIterator
        from google.api_core.page_iterator import _do_nothing_page_start
    
        project = "PROJECT"
        path = "/path/to/list/resource"
        item_to_value = mock.Mock(spec=[])
        credentials = _make_credentials()
        client = self._make_one(project=project, credentials=credentials)
        connection = client._base_connection = _make_connection()
    
>       iterator = client._list_resource(path=path, item_to_value=item_to_value,)

tests/unit/test_client.py:485: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 

self = <google.cloud.storage.client.Client object at 0x7efcfb9f3b38>
path = '/path/to/list/resource', item_to_value = <Mock id='139625018221344'>
page_token = None, max_results = None, extra_params = None
page_start = <function _do_nothing_page_start at 0x7efcfc69fae8>
page_size = None, timeout = 60
retry = <google.api_core.retry.Retry object at 0x7efcfc756c50>

    def _list_resource(
        self,
        path,
        item_to_value,
        page_token=None,
        max_results=None,
        extra_params=None,
        page_start=page_iterator._do_nothing_page_start,
        page_size=None,
        timeout=_DEFAULT_TIMEOUT,
        retry=DEFAULT_RETRY,
    ):
        api_request = functools.partial(
            self._connection.api_request, timeout=timeout, retry=retry
        )
        return page_iterator.HTTPIterator(
            client=self,
            api_request=api_request,
            path=path,
            item_to_value=item_to_value,
            page_token=page_token,
            max_results=max_results,
            extra_params=extra_params,
            page_start=page_start,
>           page_size=page_size,
        )
E       TypeError: __init__() got an unexpected keyword argument 'page_size'

google/cloud/storage/client.py:403: TypeError
__________________ TestClient.test__list_resource_w_explicit ___________________

self = <tests.unit.test_client.TestClient testMethod=test__list_resource_w_explicit>

    def test__list_resource_w_explicit(self):
        import functools
        from google.api_core.page_iterator import HTTPIterator
    
        project = "PROJECT"
        path = "/path/to/list/resource"
        item_to_value = mock.Mock(spec=[])
        page_token = "PAGE-TOKEN"
        max_results = 47
        extra_params = {"foo": "Foo"}
        page_start = mock.Mock(spec=[])
        credentials = _make_credentials()
        client = self._make_one(project=project, credentials=credentials)
        connection = client._base_connection = _make_connection()
    
        iterator = client._list_resource(
            path=path,
            item_to_value=item_to_value,
            page_token=page_token,
            max_results=max_results,
            extra_params=extra_params,
>           page_start=page_start,
        )

tests/unit/test_client.py:523: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 

self = <google.cloud.storage.client.Client object at 0x7efcfbdfe470>
path = '/path/to/list/resource', item_to_value = <Mock id='139625022614160'>
page_token = 'PAGE-TOKEN', max_results = 47, extra_params = {'foo': 'Foo'}
page_start = <Mock id='139625022612368'>, page_size = None, timeout = 60
retry = <google.api_core.retry.Retry object at 0x7efcfc756c50>

    def _list_resource(
        self,
        path,
        item_to_value,
        page_token=None,
        max_results=None,
        extra_params=None,
        page_start=page_iterator._do_nothing_page_start,
        page_size=None,
        timeout=_DEFAULT_TIMEOUT,
        retry=DEFAULT_RETRY,
    ):
        api_request = functools.partial(
            self._connection.api_request, timeout=timeout, retry=retry
        )
        return page_iterator.HTTPIterator(
            client=self,
            api_request=api_request,
            path=path,
            item_to_value=item_to_value,
            page_token=page_token,
            max_results=max_results,
            extra_params=extra_params,
            page_start=page_start,
>           page_size=page_size,
        )
E       TypeError: __init__() got an unexpected keyword argument 'page_size'

google/cloud/storage/client.py:403: TypeError


=========================== short test summary info ============================
FAILED tests/unit/test_client.py::TestClient::test__list_resource_w_defaults
FAILED tests/unit/test_client.py::TestClient::test__list_resource_w_explicit
2 failed, 1026 passed, 1 skipped in 19.16s
nox > Command py.test --quiet --cov=google.cloud.storage --cov=google.cloud --cov=tests.unit --cov-append --cov-config=.coveragerc --cov-report= --cov-fail-under=0 tests/unit failed with exit code 1
nox > Session unit-3.6 failed.

The fix would be to add ranges for google-api-core and google-auth (another transitive dependency) to setup.py, and then pin the minimum versions for those ranges in testing/constraints-3.6.txt.