Fix: handle errors on event handlers (refs: #7629)

CHANGES

@@ -103,6 +103,7 @@ Bugs fixed
 * #7628: imgconverter: runs imagemagick once unnecessary for builders not
   supporting images
 * #7610: incorrectly renders consecutive backslashes for docutils-0.16
+* #7646: handle errors on event handlers
 
 Testing
 --------

sphinx/events.py

@@ -16,7 +16,7 @@
 from typing import Any, Callable, Dict, List, NamedTuple
 
 from sphinx.deprecation import RemovedInSphinx40Warning
-from sphinx.errors import ExtensionError
+from sphinx.errors import ExtensionError, SphinxError
 from sphinx.locale import __
 from sphinx.util import logging
 
@@ -100,11 +100,17 @@ def emit(self, name: str, *args: Any) -> List:
         results = []
         listeners = sorted(self.listeners[name], key=attrgetter("priority"))
         for listener in listeners:
-            if self.app is None:
-                # for compatibility; RemovedInSphinx40Warning
-                results.append(listener.handler(*args))
-            else:
-                results.append(listener.handler(self.app, *args))
+            try:
+                if self.app is None:
+                    # for compatibility; RemovedInSphinx40Warning
+                    results.append(listener.handler(*args))
+                else:
+                    results.append(listener.handler(self.app, *args))
+            except SphinxError:
+                raise
+            except Exception as exc:
+                raise ExtensionError(__("Handler %r for event %r threw an exception") %
+                                     (listener.handler, name)) from exc
         return results
 
     def emit_firstresult(self, name: str, *args: Any) -> Any: