32-bit:

======================================================================
ERROR: test_mktime (test.test_time.TimeTestCase)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/data/prj/python/src/python3-3.7.0/Lib/test/test_time.py", line 446, in test_mktime
    self.assertEqual(time.mktime(tt), t)
OverflowError: mktime argument out of range

======================================================================
FAIL: test_pthread_getcpuclockid (test.test_time.TimeTestCase)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/data/prj/python/src/python3-3.7.0/Lib/test/test_time.py", line 129, in test_pthread_getcpuclockid
    self.assertNotEqual(clk_id, time.CLOCK_THREAD_CPUTIME_ID)
AssertionError: 12 == 12

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

64-bit:
======================================================================
ERROR: test_mktime (test.test_time.TimeTestCase)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/opt/lib/python3.7/test/test_time.py", line 446, in test_mktime
    self.assertEqual(time.mktime(tt), t)
OverflowError: mktime argument out of range

======================================================================
ERROR: test_pthread_getcpuclockid (test.test_time.TimeTestCase)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/opt/lib/python3.7/test/test_time.py", line 130, in test_pthread_getcpuclockid
    t1 = time.clock_gettime(clk_id)
OverflowError: signed integer is greater than maximum

The test_mktime failed because
time.mktime(time.localtime(-2)) -- actually any negative value in localtime - fails

The patch in the file Modules/timemodule.c fixes this.

The test_pthread_getcpuclockid is a bit more complex as the result is different
depending on 32 or 64-bit mode.

In 32-bit mode AIX always responds with the constant CLOCK_THREAD_CPUTIME_ID.
The patch in Lib/test/test_time.py makes the test aware of this.

In AIX clockid_t is actually long long. However, changing the type to parse to "L"
broke many other things. It seems to work as a long ("l") when the ABI is 64-bit.

See additional change in Modules/timemodule.c 
static PyObject *
time_clock_gettime

Finally,
added some (additional) range checking for 
_PyTime_localtime for AIX. Not having this complicated testing for above.