Update filterwarnings so test warnings are treated as errors (Fixes ENG-73)

[linkous8]

No description provided.

[linear]

ENG-73 Warnings fired by tests should cause test failures

Per @blake's request, I've worked on getting test warnings to raise errors instead as time permits since this is fairly low priority/nice to have. The change consists of updating pytest's filterwarnings config to cause all warnings to error then ignore warnings we don't care about:

[tool:pytest]
testpaths = tests
addopts = --kube-config=tests/kubeconfig --kube-context=kubetest
filterwarnings =
    error
    ignore: .*the imp module is deprecated.*:DeprecationWarning
    ignore: .*Using or importing the ABCs from 'collections':DeprecationWarning
    ignore: "@coroutine" decorator is deprecated since Python 3.8, use "async def" instead:DeprecationWarning
    ignore: The loop argument is deprecated since Python 3.8, and scheduled for removal in Python 3.10:DeprecationWarning
    ignore: Exception ignored in. <_io.FileIO \[closed\]>:pytest.PytestUnraisableExceptionWarning
    ignore: Exception ignored in. <ssl.SSLSocket fd=-1, family=AddressFamily.AF_INET, type=SocketKind.SOCK_STREAM, proto=6>:pytest.PytestUnraisableExceptionWarning
    ignore: unclosed <ssl.SSLSocket .*:ResourceWarning

Currently the above causes the integration test suite to run indefinitely and requires further debug before it can be merged (see branch https://github.com/opsani/servox/tree/bugfix/add-filterwarnings-error)

[rstarmer]

Looks good to me. Additional exceptions can always be added if they are found to be needed.