bpo-32206: Update pdb usage to include new module option (GH-5111)

Lib/pdb.py

@@ -1638,9 +1638,11 @@ def help():
     pydoc.pager(__doc__)
 
 _usage = """\
-usage: pdb.py [-c command] ... pyfile [arg] ...
+usage: pdb.py [-c command] ... [-m module | pyfile] [arg] ...
 
-Debug the Python program given by pyfile.
+Debug the Python program given by pyfile. Alternatively,
+an executable module or package to debug can be specified using
+the -m switch.
 
 Initial commands are read from .pdbrc files in your home directory
 and in the current directory, if they exist.  Commands supplied with

Lib/test/test_pdb.py

@@ -1182,7 +1182,10 @@ class PdbTestCase(unittest.TestCase):
             quit
         """
         stdout, stderr = self._run_pdb(["-m", "pdb"], commands)
-        self.assertIn("Debug the Python program given by pyfile.", stdout.splitlines())
+        self.assertIn(
+            pdb._usage,
+            stdout.replace('\r', '')  # remove \r for windows
+        )
 
     def test_module_without_a_main(self):
         module_name = 't_main'