The reason buildbots have not catched this is because the re-run login seems to not detect the problem on the second run:

./python.exe -m test test_inspect -j 1 -u all -W --slowest --fail-env-changed --timeout=11700 -R 3:3 -u-cpu -w

WARNING: Disable --verbose3 because it's incompatible with --huntrleaks: see http://bugs.python.org/issue27103
0:00:00 load avg: 2.73 Run tests in parallel using 1 child processes (timeout: 3 hour 15 min, worker timeout: 3 hour 20 min)
0:00:03 load avg: 2.92 [1/1/1] test_inspect failed (1 error)
beginning 6 repetitions
123456
.test test_inspect failed -- Traceback (most recent call last):
  File "/Users/pgalindo3/github/cpython/Lib/test/test_inspect.py", line 398, in test_getclasses
    tree = inspect.getclasstree([cls[1] for cls in classes])
  File "/Users/pgalindo3/github/cpython/Lib/inspect.py", line 1185, in getclasstree
    return walktree(roots, children, None)
  File "/Users/pgalindo3/github/cpython/Lib/inspect.py", line 1158, in walktree
    results.append(walktree(children[c], children, c))
  File "/Users/pgalindo3/github/cpython/Lib/inspect.py", line 1154, in walktree
    classes.sort(key=attrgetter('__module__', '__name__'))
TypeError: '<' not supported between instances of 'str' and 'module'

== Tests result: FAILURE ==

10 slowest tests:
- test_inspect: 3.4 sec

1 test failed:
    test_inspect

1 re-run test:
    test_inspect

0:00:03 load avg: 2.92 Re-running failed tests in verbose mode
0:00:03 load avg: 2.92 Re-running test_inspect in verbose mode (matching: test_getclasses)
beginning 6 repetitions
123456
test_getclasses (test.test_inspect.TestRetrievingSourceCode) ... ok

----------------------------------------------------------------------

Ran 1 test in 0.001s

OK
.test_getclasses (test.test_inspect.TestRetrievingSourceCode) ... ok

----------------------------------------------------------------------

Ran 1 test in 0.001s

OK
.test_getclasses (test.test_inspect.TestRetrievingSourceCode) ... ok

----------------------------------------------------------------------

Ran 1 test in 0.001s

OK
.test_getclasses (test.test_inspect.TestRetrievingSourceCode) ... ok

----------------------------------------------------------------------

Ran 1 test in 0.001s

OK
.test_getclasses (test.test_inspect.TestRetrievingSourceCode) ... ok

----------------------------------------------------------------------

Ran 1 test in 0.001s

OK
.test_getclasses (test.test_inspect.TestRetrievingSourceCode) ... ok

----------------------------------------------------------------------

Ran 1 test in 0.001s

OK
.

== Tests result: FAILURE then SUCCESS ==

1 test OK.

10 slowest tests:
- test_inspect: 3.4 sec

Total duration: 4.6 sec
Tests result: FAILURE then SUCCESS