[WIP] Mssql pyodbc

[apelade]

Work-In-Progress only, experiment for https://github.com/18F/rdbms-subsetter/issues/11 - do not accept this PR

This test can create and insert data, but gets errors when running parent and null key test cases.

• First test busy: lalchemy.exc.DBAPIError: (Error) ('HY000', '[HY000] [Microsoft][ODBC SQL Server Driver]Connection is busy with results for another hstmt (0) (SQLExecDirectW)' Maybe configure connection or db witn the non SQLExecDirect option. Or try adding nocount.
• Second one gets connection already closed, could be programming error in test, just un-commented it. Need to check when unittest tearDown gets called.

Requires creation of two ODBC datasources named in test_mssql_pyodbc.py, and probably mssql (or access?) I have been trying to run it on our big db, maybe should start with fresh empty source and dest dbs.

Full errors: https://gist.github.com/apelade/e96075e55117bca795d5

Running the rdbms-subsetter command against the big db results in a memory error . https://gist.github.com/apelade/d7f2391f8ca521552437

Test won't work for CI - travis doesn't have SQL Server yet: https://github.com/travis-ci/travis-ci/issues/216

[apelade]

haven't been able to follow up on this, closing for now