Show PEP-678 notes in ultratb (Plain), add tests

docs/source/whatsnew/pr/pep678-notes.rst

@@ -0,0 +1,5 b''
+Support for PEP-678 Exception Notes
+-----------------------------------
+
+Ultratb now shows :pep:`678` notes, improving your debugging experience on
+Python 3.11+ or with libraries such as Pytest and Hypothesis.

IPython/core/tests/test_ultratb.py

@@ -363,6 +363,29 b' def r3o2():'
             ip.run_cell("r3o2()")
 
 
+class PEP678NotesReportingTest(unittest.TestCase):
+    ERROR_WITH_NOTE = """
+try:
+    raise AssertionError("Message")
+except Exception as e:
+    try:
+        e.add_note("This is a PEP-678 note.")
+    except AttributeError:  # Python <= 3.10
+        e.__notes__ = ("This is a PEP-678 note.",)
+    raise
+    """
+
+    def test_verbose_reports_notes(self):
+        with tt.AssertPrints(["AssertionError", "Message", "This is a PEP-678 note."]):
+            ip.run_cell(self.ERROR_WITH_NOTE)
+
+    def test_plain_reports_notes(self):
+        with tt.AssertPrints(["AssertionError", "Message", "This is a PEP-678 note."]):
+            ip.run_cell("%xmode Plain")
+            ip.run_cell(self.ERROR_WITH_NOTE)
+            ip.run_cell("%xmode Verbose")
+
+
 #----------------------------------------------------------------------------
 
 # module testing (minimal)

IPython/core/ultratb.py

@@ -686,6 +686,9 b' class ListTB(TBTools):'
             else:
                 list.append('%s\n' % stype)
 
+            # PEP-678 notes
+            list.extend(f"{x}\n" for x in getattr(value, "__notes__", []))
+
         # sync with user hooks
         if have_filedata:
             ipinst = get_ipython()