GH-113661: unittest runner: Don't exit 5 if tests were skipped (#113856)

The intention of exiting 5 was to detect issues where the test suite
wasn't discovered at all. If we skipped tests, it was correctly
discovered.

Lib/test/test_unittest/test_program.py

@@ -167,6 +167,18 @@ class Test_TestProgram(unittest.TestCase):
                     'expected failures=1, unexpected successes=1)\n')
         self.assertTrue(out.endswith(expected))
 
+    def test_ExitSkippedSuite(self):
+        stream = BufferedWriter()
+        with self.assertRaises(SystemExit) as cm:
+            unittest.main(
+                argv=["foobar", "-k", "testSkipped"],
+                testRunner=unittest.TextTestRunner(stream=stream),
+                testLoader=self.TestLoader(self.FooBar))
+        self.assertEqual(cm.exception.code, 0)
+        out = stream.getvalue()
+        expected = '\n\nOK (skipped=1)\n'
+        self.assertTrue(out.endswith(expected))
+
     def test_ExitEmptySuite(self):
         stream = BufferedWriter()
         with self.assertRaises(SystemExit) as cm:

Lib/unittest/main.py

@@ -269,7 +269,7 @@ class TestProgram(object):
             testRunner = self.testRunner
         self.result = testRunner.run(self.test)
         if self.exit:
-            if self.result.testsRun == 0:
+            if self.result.testsRun == 0 and len(self.result.skipped) == 0:
                 sys.exit(_NO_TESTS_EXITCODE)
             elif self.result.wasSuccessful():
                 sys.exit(0)

Lib/unittest/runner.py

@@ -274,7 +274,7 @@ class TextTestRunner(object):
                 infos.append("failures=%d" % failed)
             if errored:
                 infos.append("errors=%d" % errored)
-        elif run == 0:
+        elif run == 0 and not skipped:
             self.stream.write("NO TESTS RAN")
         else:
             self.stream.write("OK")