Queries

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- Narrow the pin to psycopg2 < 2.8 due to a breaking change
- Fix Results iterator for Python 3.7 (31 - `nvllsvm <https://github.com/nvllsvm>`_)

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- REMOVED support for Python 2.6
- FIXED CPU Pegging bug: Cleanup IOLoop and internal stack in ``TornadoSession`` on connection error. In the case of a connection error, the failure to do this caused CPU to peg 100% utilization looping on a non-existent file descriptor. Thanks to `cknave <https://github.com/cknave>`_ for his work on identifying the issue, proposing a fix, and writing a working test case.
- Move the integration tests to use a local docker development environment
- Added new methods ``queries.pool.Pool.report`` and ``queries.pool.PoolManager.Report`` for reporting pool status.
- Added new methods to ``queries.pool.Pool`` for returning a list of busy, closed, executing, and locked connections.

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- Implement ``Results.__bool__`` to be explicit about Python 3 support.
- Catch any exception raised when using TornadoSession and invoking the execute function in psycopg2 for exceptions raised prior to sending the query to Postgres.
This could be psycopg2.Error, IndexError, KeyError, or who knows, it's not documented in psycopg2.

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- Remove the functionality from ``TornadoSession.validate`` and make it raise a ``DeprecationWarning``
- Catch the ``KeyError`` raised when ``PoolManager.clean()`` is invoked for a pool that doesn't exist

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- Ensure the pool exists when executing a query in TornadoSession, the new timeout behavior prevented that from happening.

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- Use an absolute time in the call to ``add_timeout``