Add quick comment and improve CHANGELOG a bit

Author: nicoddemus

changelog/5811.bugfix.rst

@@ -1 +1 @@
-Handle --fulltrace with pytest.raises.
+Handle ``--fulltrace`` correctly with ``pytest.raises``.

src/_pytest/nodes.py

@@ -272,12 +272,15 @@ def _repr_failure_py(self, excinfo, style=None):
         except OSError:
             abspath = True
 
+        # traceback has been pruned at this point already if not in --fulltrace mode
+        tbfilter = False
+
         return excinfo.getrepr(
             funcargs=True,
             abspath=abspath,
             showlocals=self.config.getoption("showlocals", False),
             style=style,
-            tbfilter=False,
+            tbfilter=tbfilter,
             truncate_locals=truncate_locals,
         )