gh-152558: Avoid redundant quoting in subprocess.TimeoutExpired.__str__

Lib/subprocess.py

@@ -180,8 +180,7 @@ def __init__(self, cmd, timeout, output=None, stderr=None):
         self.stderr = stderr
 
     def __str__(self):
-        return ("Command '%s' timed out after %s seconds" %
-                (self.cmd, self.timeout))
+        return f"Command {self.cmd!r} timed out after {self.timeout} seconds"
 
     @property
     def stdout(self):

Lib/test/test_subprocess.py

@@ -2449,6 +2449,19 @@ def test_CalledProcessError_str(self):
         err = subprocess.CalledProcessError(-9876543, "fake cmd")
         self.assertEqual(str(err), "Command 'fake cmd' died with unknown signal 9876543.")
 
+    def test_TimeoutExpired_str(self):
+        # timeout command string
+        err = subprocess.TimeoutExpired("fake cmd", 1)
+        self.assertEqual(str(err), "Command 'fake cmd' timed out after 1 seconds")
+
+        # timeout command string with a single-quote
+        err = subprocess.TimeoutExpired("fake ' cmd", 1)
+        self.assertEqual(str(err), 'Command "fake \' cmd" timed out after 1 seconds')
+
+        # timeout command list
+        err = subprocess.TimeoutExpired(["fake", "cmd"], 1)
+        self.assertEqual(str(err), "Command ['fake', 'cmd'] timed out after 1 seconds")
+
     def test_preexec(self):
         # DISCLAIMER: Setting environment variables is *not* a good use
         # of a preexec_fn.  This is merely a test.

Misc/NEWS.d/next/Library/2026-06-29-16-30-58.gh-issue-152558.CCfp-R.rst

@@ -0,0 +1 @@
+Avoid redundant quoting in :exc:`subprocess.TimeoutExpired` messages.