Add pytest-aiohttp development dep to svi_client

[aaraney]

fixes #217

Additions

• Adds pytest-aiohttp development dependency to svi_client

Testing

1. Verified that this resolves locally RuntimeError: There is no current event loop in thread 'MainThread'. thrown in slow unit tests.

Checklist

• PR has an informative and human-readable title
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• Changes are limited to a single goal (no scope creep)
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• Code follows project standards (see CONTRIBUTING.md)
• Passes all existing automated tests
• Any change in functionality is tested
• New functions are documented (with a description, list of inputs, and expected output) using numpy docstring formatting
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[aaraney]

Weird, looks like a NWMFileProcessor test is failing.

[aaraney]

Looks like the xarray.backends.plugins.list_engines function is throwing a exception because an EntryPoints object doenst have a method im assuming it previously had. Im going to throw this into its own issue and track it there.