pythongh-131591: Add tests for _PdbClient (python#132976)

Author: godlygeek

Lib/pdb.py

@@ -2716,7 +2716,7 @@ def _read_reply(self):
             try:
                 payload = json.loads(msg)
             except json.JSONDecodeError:
-                self.error(f"Disconnecting: client sent invalid JSON {msg}")
+                self.error(f"Disconnecting: client sent invalid JSON {msg!r}")
                 raise EOFError
 
             match payload:
@@ -3023,7 +3023,7 @@ def cmdloop(self):
                     payload = json.loads(payload_bytes)
                 except json.JSONDecodeError:
                     print(
-                        f"*** Invalid JSON from remote: {payload_bytes}",
+                        f"*** Invalid JSON from remote: {payload_bytes!r}",
                         flush=True,
                     )
                     continue