The first part of my telnetlib work is testing what already is. 
Attached is a patch to test_telnetlib that tests mosts of the guarantees
of the telnetlib.Telnet.read_* methods (as guaranteed by the docs, at
least).

Theoretically every test I added has a race condition.
ReadTests.blocking_timeout is currently set to 0.1 seconds and works on
my platform (it also works at 0.0 seconds).  Is this acceptable or do I
need to include semaphores will 100% predictable behavior?

TIA