Before committing, I experimented with disabling test/test_idle. The simple and safe method is to comment out the 'load_tests' line. With no tests discovered, all pass ;-). Without verbosity, there is no indication that there were none. A little harder, and needing to be tested for typos before committing, is to add this line before that line:
  import unittest; raise unittest.SkipTest('skip for buildbots')
Regrtest (py -m test test_idle) registers the unexpected skip. Unittest (py -m test.test_idle) exits with a traceback. This is recorded in an updated README, which also incorporates Todd's suggestion. I also touched up test/test_idle.py.

If buildbots do not break, I will work on 2.7.