Fix ResourceWarning from unclosed files in ichnaea tests

[jwhitlock]

With warnings enabled (make testshell, and pytest -Wd ichnaea), there are warnings about unclosed files:

ichnaea/api/submit/tests/test_submit_v1.py::TestView::test_batches
  /app/ichnaea/api/submit/tests/test_submit_v1.py:240: ResourceWarning: unclosed file <_io.BufferedRandom name=14>
    {

ichnaea/api/submit/tests/test_submit_v2.py::TestView::test_batches
  /usr/local/lib/python3.8/site-packages/sqlalchemy/event/attr.py:319: ResourceWarning: unclosed file <_io.BufferedRandom name=14>
    for fn in self.parent_listeners:

ichnaea/content/tests/test_views.py::TestFunctionalContent::test_content[/stats/regions-200-stats.regions-1]
  /usr/local/lib/python3.8/site-packages/chameleon/astutil.py:48: ResourceWarning: unclosed file <_io.BufferedRandom name=14>
    return compile(source, '', mode, ast.PyCF_ONLY_AST)

Further research is needed to determine if this is a issue with test setup and teardown, or if this may be causing problems in production as well. This stack overflow answer has some tips for investigating this issue.

Originally filed as bug 1650870 on 2020-07-06

[jwhitlock]

With platform linux -- Python 3.9.1, pytest-6.2.2, py-1.9.0, pluggy-0.13.1:

ichnaea/api/submit/tests/test_submit_v1.py::TestView::test_batches
  /app/ichnaea/api/submit/tests/test_submit_v1.py:243: ResourceWarning: unclosed file <_io.BufferedRandom name=14>
    "wifiAccessPoints": [{"macAddress": wifi.mac}],

ichnaea/api/submit/tests/test_submit_v2.py::TestView::test_batches
  /app/ichnaea/api/schema.py:106: ResourceWarning: unclosed file <_io.BufferedRandom name=14>
    result = super(RenamingMapping, self)._impl(node, *args, **kw)

ichnaea/webapp/tests.py::TestHeartbeatErrors::test_database
  /usr/local/lib/python3.9/site-packages/pyramid/viewderivers.py:163: ResourceWarning: unclosed file <_io.BufferedRandom name=15>
    wrapper_view = wrapper(view, info)

[jwhitlock]

The Waitress 2.1.0 Release Notes include a note about closing bytestreams:

Fixed an issue whereby BytesIO objects were not properly closed, and thereby would not get cleaned up until garbage collection would get around to it.

This led to potential for random memory spikes/memory issues, see Pylons/waitress#358 and Pylons/waitress#357.

With thanks to Florian Schulze for testing/vaidating this fix!

Running with Waitress 2.1.1 from #1807 did not fix it:

> make testshell
...
$ pytest -Wd ichnaea
...
================================================ warnings summary ================================================
<frozen importlib._bootstrap>:914: 11 warnings
ichnaea/api/locate/tests/test_blue.py: 1 warning
ichnaea/api/locate/tests/test_locate_v1.py: 1 warning
ichnaea/content/tests/test_views.py: 1 warning
ichnaea/data/tests/test_area.py: 1 warning
ichnaea/scripts/tests/test_datamap.py: 1 warning
ichnaea/taskapp/tests.py: 1 warning
ichnaea/webapp/tests.py: 1 warning
  <frozen importlib._bootstrap>:914: ImportWarning: _SixMetaPathImporter.find_spec() not found; falling back to find_module()

ichnaea/api/submit/tests/test_submit_v1.py::TestView::test_batches
  /usr/local/lib/python3.10/json/decoder.py:353: ResourceWarning: unclosed file <_io.BufferedRandom name=14>
    obj, end = self.scan_once(s, idx)

ichnaea/api/submit/tests/test_submit_v2.py::TestView::test_batches
  /usr/local/lib/python3.10/json/decoder.py:353: ResourceWarning: unclosed file <_io.BufferedRandom name=15>
    obj, end = self.scan_once(s, idx)

ichnaea/data/tests/test_station.py::TestBlue::test_block_consistent_obs[ReportSource.query-ReportSource.gnss]
  /usr/local/lib/python3.10/site-packages/sqlalchemy/orm/query.py:4422: ResourceWarning: unclosed file <_io.BufferedRandom name=14>
    _instance = loading._instance_processor(

-- Docs: https://docs.pytest.org/en/stable/how-to/capture-warnings.html

I'm pretty sure the needed fix is in our code.