[Twisted-Python] SerialPort testing on the Twisted build slaves

[Michael Thompson]

Hi,
   Ticket  http://twistedmatrix.com/trac/ticket/3690 is adding some
serial port testing. The patch adds code to discover serial ports on
Windows and Posix and the test uses the first serial port that is
discovered.

Will this approach work for the build slaves, or is it better to use
an environment variable that can be set for each build slave?

Do any of the build slaves have serial ports or are they all VMs?

Michael