Example:
https://travis-ci.org/github/python/cpython/jobs/672698615

Output:
===========================================
0:09:01 load avg: 3.96 [104/421/1] test_distutils failed -- running: test_multiprocessing_forkserver (1 min 13 sec), test_unparse (6 min 21 sec)

Warning -- files was modified by test_distutils

  Before: []

  After:  ['_configtest.gcno'] 

test test_distutils failed -- Traceback (most recent call last):

  File "/home/travis/build/python/cpython/Lib/distutils/tests/test_build_ext.py", line 112, in test_build_ext

    assert_python_ok('-c', code)

  File "/home/travis/build/python/cpython/Lib/test/support/script_helper.py", line 156, in assert_python_ok

    return _assert_python(True, *args, **env_vars)

  File "/home/travis/build/python/cpython/Lib/test/support/script_helper.py", line 142, in _assert_python

    res.fail(cmd_line)

  File "/home/travis/build/python/cpython/Lib/test/support/script_helper.py", line 70, in fail

    raise AssertionError("Process return code is %d\n"

AssertionError: Process return code is 1

command line: ['/home/travis/build/python/cpython/python', '-X', 'faulthandler', '-I', '-c', "\ntmp_dir = '/tmp/tmp3y4hpawx'\n\nimport sys\nimport unittest\nfrom test import support\n\nsys.path.insert(0, tmp_dir)\nimport xx\n\nclass Tests(unittest.TestCase):\n    def test_xx(self):\n        for attr in ('error', 'foo', 'new', 'roj'):\n            self.assertTrue(hasattr(xx, attr))\n\n        self.assertEqual(xx.foo(2, 5), 7)\n        self.assertEqual(xx.foo(13,15), 28)\n        self.assertEqual(xx.new().demo(), None)\n        if support.HAVE_DOCSTRINGS:\n            doc = 'This is a template module just for instruction.'\n            self.assertEqual(xx.__doc__, doc)\n        self.assertIsInstance(xx.Null(), xx.Null)\n        self.assertIsInstance(xx.Str(), xx.Str)\n\n\nunittest.main()\n"]

stdout:

---

---

stderr:

---

Traceback (most recent call last):

  File "<string>", line 9, in <module>

ImportError: /tmp/tmp3y4hpawx/xx.cpython-39-x86_64-linux-gnu.so: undefined symbol: __gcov_merge_add

---

===========================================

Python is built GCC with -ftest-coverage option. But it seems like this option is "leaked" to C flags used to build third party extensions in distutils.

Maybe CFLAGS_NODIST should be used instead of CFLAGS.

The Travis CI job runs these commands:
---
./configure
xvfb-run make -j4 coverage-report
make pythoninfo
bash <(curl -s https://codecov.io/bash) -y .github/codecov.yml
---