Uninteresting bits of the output elided:

C:\Data\code\CPython\hg.python.org\default>python -m test -vn test_os
Running Debug|Win32 interpreter...
== CPython 3.5.0a3+ (default:0b3027a2abbc, Apr 11 2015, 21:11:57) [MSC v.1900 32
 bit (Intel)]
==   Windows-post2012Server-6.3.9600 little-endian
==   hash algorithm: siphash24 32bit
==   C:\Data\code\CPython\hg.python.org\default\build\test_python_4312
Testing with flags: sys.flags(debug=0, inspect=0, interactive=0, optimize=0, don
t_write_bytecode=0, no_user_site=0, no_site=0, ignore_environment=0, verbose=0,
bytes_warning=0, quiet=0, hash_randomization=1, isolated=0)
[1/1] test_os
...
test_bad_fd (test.test_os.DeviceEncodingTests) ... minkernel\crts\ucrt\src\appcrt\lowio\osfinfo.cpp(257) : Assertion failed: fh >= 0 && (unsigned)fh < (unsigned)_nhandle
ok
...
test_closerange (test.test_os.FileTests) ... minkernel\crts\ucrt\src\appcrt\lowio\osfinfo.cpp(258) : Assertion failed: _osfile(fh) & FOPEN
minkernel\crts\ucrt\src\appcrt\lowio\osfinfo.cpp(258) : Assertion failed: _osfile(fh) & FOPEN
ok
...
test_15261 (test.test_os.StatAttributeTests) ... minkernel\crts\ucrt\src\appcrt\lowio\osfinfo.cpp(258) : Assertion failed: _osfile(fh) & FOPEN
ok
...
test_stty_match (test.test_os.TermsizeTests)
Check if stty returns the same results ... minkernel\crts\ucrt\src\appcrt\lowio\osfinfo.cpp(257) : Assertion failed: fh >= 0 && (unsigned)fh < (unsigned)_nhandle
skipped 'stty invocation failed'
...
test_closerange (test.test_os.TestInvalidFD) ... minkernel\crts\ucrt\src\appcrt\lowio\osfinfo.cpp(258) : Assertion failed: _osfile(fh) & FOPEN
minkernel\crts\ucrt\src\appcrt\lowio\osfinfo.cpp(258) : Assertion failed: _osfile(fh) & FOPEN
minkernel\crts\ucrt\src\appcrt\lowio\osfinfo.cpp(258) : Assertion failed: _osfile(fh) & FOPEN
minkernel\crts\ucrt\src\appcrt\lowio\osfinfo.cpp(258) : Assertion failed: _osfile(fh) & FOPEN
minkernel\crts\ucrt\src\appcrt\lowio\osfinfo.cpp(258) : Assertion failed: _osfile(fh) & FOPEN
minkernel\crts\ucrt\src\appcrt\lowio\osfinfo.cpp(258) : Assertion failed: _osfile(fh) & FOPEN
minkernel\crts\ucrt\src\appcrt\lowio\osfinfo.cpp(258) : Assertion failed: _osfile(fh) & FOPEN
minkernel\crts\ucrt\src\appcrt\lowio\osfinfo.cpp(258) : Assertion failed: _osfile(fh) & FOPEN
minkernel\crts\ucrt\src\appcrt\lowio\osfinfo.cpp(258) : Assertion failed: _osfile(fh) & FOPEN
minkernel\crts\ucrt\src\appcrt\lowio\osfinfo.cpp(258) : Assertion failed: _osfile(fh) & FOPEN
minkernel\crts\ucrt\src\appcrt\lowio\osfinfo.cpp(258) : Assertion failed: _osfile(fh) & FOPEN
minkernel\crts\ucrt\src\appcrt\lowio\osfinfo.cpp(258) : Assertion failed: _osfile(fh) & FOPEN
minkernel\crts\ucrt\src\appcrt\lowio\osfinfo.cpp(258) : Assertion failed: _osfile(fh) & FOPEN
minkernel\crts\ucrt\src\appcrt\lowio\osfinfo.cpp(258) : Assertion failed: _osfile(fh) & FOPEN
minkernel\crts\ucrt\src\appcrt\lowio\osfinfo.cpp(258) : Assertion failed: _osfile(fh) & FOPEN
minkernel\crts\ucrt\src\appcrt\lowio\osfinfo.cpp(258) : Assertion failed: _osfile(fh) & FOPEN
minkernel\crts\ucrt\src\appcrt\lowio\osfinfo.cpp(258) : Assertion failed: _osfile(fh) & FOPEN
minkernel\crts\ucrt\src\appcrt\lowio\osfinfo.cpp(258) : Assertion failed: _osfile(fh) & FOPEN
ok
test_dup (test.test_os.TestInvalidFD) ... minkernel\crts\ucrt\src\appcrt\lowio\osfinfo.cpp(258) : Assertion failed: _osfile(fh) & FOPEN
ok
test_dup2 (test.test_os.TestInvalidFD) ... minkernel\crts\ucrt\src\appcrt\lowio\osfinfo.cpp(258) : Assertion failed: _osfile(fh) & FOPEN
ok
...
test_fdopen (test.test_os.TestInvalidFD) ... minkernel\crts\ucrt\src\appcrt\lowio\osfinfo.cpp(258) : Assertion failed: _osfile(fh) & FOPEN
ok
...
test_fstat (test.test_os.TestInvalidFD) ... minkernel\crts\ucrt\src\appcrt\lowio\osfinfo.cpp(258) : Assertion failed: _osfile(fh) & FOPEN
ok
...
test_fsync (test.test_os.TestInvalidFD) ... minkernel\crts\ucrt\src\appcrt\lowio\osfinfo.cpp(258) : Assertion failed: _osfile(fh) & FOPEN
ok
...
test_inheritable (test.test_os.TestInvalidFD) ... minkernel\crts\ucrt\src\appcrt\lowio\osfinfo.cpp(258) : Assertion failed: _osfile(fh) & FOPEN
minkernel\crts\ucrt\src\appcrt\lowio\osfinfo.cpp(258) : Assertion failed: _osfile(fh) & FOPEN
ok
test_isatty (test.test_os.TestInvalidFD) ... minkernel\crts\ucrt\src\appcrt\lowio\osfinfo.cpp(258) : Assertion failed: _osfile(fh) & FOPEN
ok
test_lseek (test.test_os.TestInvalidFD) ... minkernel\crts\ucrt\src\appcrt\lowio\osfinfo.cpp(258) : Assertion failed: _osfile(fh) & FOPEN
ok
test_read (test.test_os.TestInvalidFD) ... minkernel\crts\ucrt\src\appcrt\lowio\osfinfo.cpp(258) : Assertion failed: _osfile(fh) & FOPEN
ok
...
test_write (test.test_os.TestInvalidFD) ... minkernel\crts\ucrt\src\appcrt\lowio\osfinfo.cpp(258) : Assertion failed: _osfile(fh) & FOPEN
ok
...

----------------------------------------------------------------------
Ran 189 tests in 7.424s

OK (skipped=75)
1 test OK.