[3.9] bpo-43776: Remove list call from args in Popen repr (GH-25338) (GH-26510)

Removes the `list` call in the Popen `repr`.

Current implementation:

For cmd = `python --version`,  with `shell=True`.

```bash
<Popen: returncode: None args: ['p', 'y', 't', 'h', 'o', 'n', ' ', '-', '-',...>
```

For `shell=False` and args=`['python', '--version']`, the output is correct:

```bash
<Popen: returncode: None args: ['python', '--version']>
```

With the new changes the `repr`  yields:

For cmd = `python --version`,  with `shell=True`:

```bash
<Popen: returncode: None args: 'python --version'>
```

For `shell=False` and args=`['python', '--version']`, the output:

```bash
<Popen: returncode: None args: ['python', '--version']>
```

Automerge-Triggered-By: GH:gpshead.
(cherry picked from commit db0c5b786d)

Co-authored-by: M. Kocher <michael.kocher@me.com>

Co-authored-by: M. Kocher <michael.kocher@me.com>

Lib/test/test_subprocess.py

@@ -20,6 +20,7 @@ import threading
 import gc
 import textwrap
 import json
+import pathlib
 from test.support import FakePath
 
 try:
@@ -1373,28 +1374,23 @@ class ProcessTestCase(BaseTestCase):
         p.communicate(b"x" * 2**20)
 
     def test_repr(self):
-        # Run a command that waits for user input, to check the repr() of
-        # a Proc object while and after the sub-process runs.
-        code = 'import sys; input(); sys.exit(57)'
-        cmd = [sys.executable, '-c', code]
-        result = "<Popen: returncode: {}"
+        path_cmd = pathlib.Path("my-tool.py")
+        pathlib_cls = path_cmd.__class__.__name__
 
-        with subprocess.Popen(
-                cmd, stdin=subprocess.PIPE, universal_newlines=True) as proc:
-            self.assertIsNone(proc.returncode)
-            self.assertTrue(
-                repr(proc).startswith(result.format(proc.returncode)) and
-                repr(proc).endswith('>')
-            )
-
-            proc.communicate(input='exit...\n')
-            proc.wait()
-
-            self.assertIsNotNone(proc.returncode)
-            self.assertTrue(
-                repr(proc).startswith(result.format(proc.returncode)) and
-                repr(proc).endswith('>')
-            )
+        cases = [
+            ("ls", True, 123, "<Popen: returncode: 123 args: 'ls'>"),
+            ('a' * 100, True, 0,
+             "<Popen: returncode: 0 args: 'aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa...>"),
+            (["ls"], False, None, "<Popen: returncode: None args: ['ls']>"),
+            (["ls", '--my-opts', 'a' * 100], False, None,
+             "<Popen: returncode: None args: ['ls', '--my-opts', 'aaaaaaaaaaaaaaaaaaaaaaaa...>"),
+            (path_cmd, False, 7, f"<Popen: returncode: 7 args: {pathlib_cls}('my-tool.py')>")
+        ]
+        with unittest.mock.patch.object(subprocess.Popen, '_execute_child'):
+            for cmd, shell, code, sx in cases:
+                p = subprocess.Popen(cmd, shell=shell)
+                p.returncode = code
+                self.assertEqual(repr(p), sx)
 
     def test_communicate_epipe_only_stdin(self):
         # Issue 10963: communicate() should hide EPIPE