Logger returns NameError in non-interactive mode for Python 2

`pytest -s tests/test_noninteractive_mode` shows the following warning:
```Exception ignored in:
Traceback (most recent call last):
File "/Users/ellbosch/Repos/mssql-cli/mssqlcli/mssql_cli.py", line 196, in __del__
File "/Users/ellbosch/Repos/mssql-cli/mssqlcli/sqltoolsclient.py", line 90, in shutdown
File "/Users/ellbosch/Repos/mssql-cli/mssqlcli/jsonrpc/jsonrpcclient.py", line 184, in shutdown
File "/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/logging/__init__.py", line 1378, in info
File "/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/logging/__init__.py", line 1514, in _log
File "/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/logging/__init__.py", line 1524, in handle
File "/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/logging/__init__.py", line 1586, in callHandlers
File "/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/logging/__init__.py", line 894, in handle
File "/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/logging/__init__.py", line 1126, in emit
File "/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/logging/__init__.py", line 1116, in _open
NameError: name 'open' is not defined
```

Looks like the logger is referenced post-deconstruction.

Start by running pytest -s tests/test_noninteractive_mode, then inspect mssqlcli/mssql_cli.py at __del__, mssqlcli/sqltoolsclient.py at shutdown, and mssqlcli/jsonrpc/jsonrpcclient.py at its logging call. Confirm the teardown path can run during interpreter deconstruction, and consider the issue done when the test no longer emits the NameError warning.

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