Fixes issue #15507: test_subprocess's test_send_signal could fail if the test

runner were run in an environment where the process inherited an ignore
setting for SIGINT.  Restore the SIGINT handler to the desired
KeyboardInterrupt raising one during that test.

Lib/test/test_subprocess.py

@@ -1398,16 +1398,22 @@ class POSIXProcessTestCase(BaseTestCase):
     def _kill_process(self, method, *args):
         # Do not inherit file handles from the parent.
         # It should fix failures on some platforms.
-        p = subprocess.Popen([sys.executable, "-c", """if 1:
-                             import sys, time
-                             sys.stdout.write('x\\n')
-                             sys.stdout.flush()
-                             time.sleep(30)
-                             """],
-                             close_fds=True,
-                             stdin=subprocess.PIPE,
-                             stdout=subprocess.PIPE,
-                             stderr=subprocess.PIPE)
+        # Also set the SIGINT handler to the default to make sure it's not
+        # being ignored (some tests rely on that.)
+        old_handler = signal.signal(signal.SIGINT, signal.default_int_handler)
+        try:
+            p = subprocess.Popen([sys.executable, "-c", """if 1:
+                                 import sys, time
+                                 sys.stdout.write('x\\n')
+                                 sys.stdout.flush()
+                                 time.sleep(30)
+                                 """],
+                                 close_fds=True,
+                                 stdin=subprocess.PIPE,
+                                 stdout=subprocess.PIPE,
+                                 stderr=subprocess.PIPE)
+        finally:
+            signal.signal(signal.SIGINT, old_handler)
         # Wait for the interpreter to be completely initialized before
         # sending any signal.
         p.stdout.read(1)

Misc/NEWS

@@ -309,6 +309,11 @@ IDLE
 Tests
 -----
 
+- Issue #15507: test_subprocess's test_send_signal could fail if the test
+  runner were run in an environment where the process inherited an ignore
+  setting for SIGINT.  Restore the SIGINT handler to the desired
+  KeyboardInterrupt raising one during that test.
+
 - Issue #18792: Use "127.0.0.1" or "::1" instead of "localhost" as much as
   possible, since "localhost" goes through a DNS lookup under recent Windows
   versions.