$ python find_blocking_processes.py
Traceback (most recent call last):
File "find_blocking_processes.py", line 77, in <module>
find_blocking_processes(brokerConn)
File "find_blocking_processes.py", line 67, in find_blocking_processes
) x""").fetchall()
pyodbc.ProgrammingError: ('42000', '[42000] [FreeTDS][SQL Server]Unicode data in a Unicode-only collation or ntext data cannot be sent to clients using DB-Library (such as ISQL) or ODBC version 3.7 or earlier. (4004) (SQLExecDirectW)')

After a bit of digging, it appears that you need to tell the ODBC driver which protocol to talk to a server in. Rectifying this was pretty straight forward:

In the file /etc/freetds.conf I added a line to the serverconfig  stating to use the version 8.0 protocol:

# A typical Microsoft SQL Server 2008 configuration
[DEVDATABASE]
host = 10.10.10.100
port = 1433
tds version = 8.0

Then in the file /etc/odbc.ini I added a line for the version as well:

[DEVDATABASE]
Driver          = /usr/lib64/libtdsodbc.so.0
Server          = 10.10.10.100
Port            = 1433
Trace           = Yes
TraceFile       = /tmp/freetdssql-foobar.log
tds_version     = 8.0

* Note the ‘_’ in the tds_version  variable in the odbc.ini

After this, the database call ran like a dream.

These were the links that pointed me in the right direction to solve this issue and contain a little more information on the causes of this:

• FreeTDS Error while trying to retrieve information from an ntext field – http://www.ubuntitis.com/?p=64
• PyODBC, UnixODBC, FreeTDS – config – http://kipb7.wordpress.com/2008/06/12/pyodbc-unixodbc-freetds-config/