Fix error tab completing in the debugger

I think I broke this in 5.2.

Closes gh-10222

IPython/terminal/debugger.py

@@ -20,13 +20,16 b' class TerminalPdb(Pdb):'
         def get_prompt_tokens(cli):
             return [(Token.Prompt, self.prompt)]
 
+        def patch_stdout(**kwargs):
+            return self.pt_cli.patch_stdout_context(**kwargs)
+
         if self._ptcomp is None:
             compl = IPCompleter(shell=self.shell,
                                         namespace={},
                                         global_namespace={},
                                         parent=self.shell,
                                        )
-            self._ptcomp = IPythonPTCompleter(compl)
+            self._ptcomp = IPythonPTCompleter(compl, patch_stdout=patch_stdout)
 
         self._pt_app = create_prompt_application(
                             editing_mode=getattr(EditingMode, self.shell.editing_mode.upper()),

IPython/terminal/interactiveshell.py

@@ -233,11 +233,15 b' class TerminalInteractiveShell(InteractiveShell):'
 
         editing_mode = getattr(EditingMode, self.editing_mode.upper())
 
+        def patch_stdout(**kwargs):
+            return self.pt_cli.patch_stdout_context(**kwargs)
+
         self._pt_app = create_prompt_application(
                             editing_mode=editing_mode,
                             key_bindings_registry=kbmanager.registry,
                             history=history,
-                            completer=IPythonPTCompleter(shell=self),
+                            completer=IPythonPTCompleter(shell=self,
+                                                    patch_stdout=patch_stdout),
                             enable_history_search=True,
                             style=style,
                             mouse_support=self.mouse_support,

IPython/terminal/ptutils.py

@@ -20,11 +20,14 b' import pygments.lexers as pygments_lexers'
 
 class IPythonPTCompleter(Completer):
     """Adaptor to provide IPython completions to prompt_toolkit"""
-    def __init__(self, ipy_completer=None, shell=None):
+    def __init__(self, ipy_completer=None, shell=None, patch_stdout=None):
         if shell is None and ipy_completer is None:
             raise TypeError("Please pass shell=an InteractiveShell instance.")
         self._ipy_completer = ipy_completer
         self.shell = shell
+        if patch_stdout is None:
+            raise TypeError("Please pass patch_stdout")
+        self.patch_stdout = patch_stdout
 
     @property
     def ipy_completer(self):
@@ -40,7 +43,7 b' class IPythonPTCompleter(Completer):'
         # Some bits of our completion system may print stuff (e.g. if a module
         # is imported). This context manager ensures that doesn't interfere with
         # the prompt.
-        with self.shell.pt_cli.patch_stdout_context():
+        with self.patch_stdout():
             used, matches = self.ipy_completer.complete(
                                 line_buffer=document.current_line,
                                 cursor_pos=document.cursor_position_col