Add SMTP error handling

• Configured admin email addresses will get an email notification with the stacktrace on unhandled exceptions.

invenio_config_tuw/ext.py

 # -*- coding: utf-8 -*-
 #
-# Copyright (C) 2020 - 2021 TU Wien.
+# Copyright (C) 2020-2022 TU Wien.
 #
 # Invenio-Config-TUW is free software; you can redistribute it and/or modify
 # it under the terms of the MIT License; see LICENSE file for more details.
@@ -8,12 +8,16 @@
 """Invenio module containing some customizations and configuration for TU Wien."""
 
 from functools import partial
+from logging.handlers import SMTPHandler
 
 from flask_security.signals import user_registered
+from invenio_mail import InvenioMail
 
 from . import config
 from .auth.utils import auto_trust_user
+from .formatters import CustomFormatter
 from .permissions import TUWCommunitiesPermissionPolicy
+from .utils import remove_duplicate_smtp_handlers
 
 
 @user_registered.connect
@@ -40,6 +44,13 @@ class InvenioConfigTUW(object):
         self.init_config(app)
         app.extensions["invenio-config-tuw"] = self
         self.override_communities_permissions(app)
+        # Ensure that invenio_mail is registered in the app.
+        if "invenio-mail" not in app.extensions:
+            InvenioMail(app)
+        # Email error handling should occur only in production mode.
+        if not app.debug and not app.testing:
+            self.register_smtp_error_handler(app)
+            remove_duplicate_smtp_handlers(app.logger)
 
     def init_config(self, app):
         """Initialize configuration."""
@@ -77,3 +88,37 @@ class InvenioConfigTUW(object):
             )
             override_func = partial(self.override_communities_permissions, app)
             app.before_first_request_funcs.append(override_func)
+
+    def register_smtp_error_handler(self, app):
+        """Register email error handler to the application."""
+        # Check if mail server and admin(s) email(s) are present in the config
+        # If not raise a warning
+        if app.config.get("MAIL_SERVER") and app.config.get("MAIL_ADMIN"):
+            # Configure Auth
+            auth = None
+            if app.config.get("MAIL_USERNAME") and app.config.get("MAIL_PASSWORD"):
+                auth = (app.config["MAIL_USERNAME"], app.config["MAIL_PASSWORD"])
+            # Configure TLS
+            secure = None
+            if app.config.get("MAIL_USE_TLS"):
+                secure = ()
+
+            # Initialize SMTP Handler
+            mail_handler = SMTPHandler(
+                mailhost=(app.config["MAIL_SERVER"], app.config.get("MAIL_PORT", 25)),
+                fromaddr=app.config["SECURITY_EMAIL_SENDER"],
+                toaddrs=app.config["MAIL_ADMIN"],
+                subject=app.config["THEME_SITENAME"] + " - Failure",
+                credentials=auth,
+                secure=secure
+            )
+            # level 40 is for ERROR. See python's logging for further mappings.
+            mail_handler.setLevel(40)
+            # add custom formatter
+            mail_handler.setFormatter(CustomFormatter())
+            # Attach to the application
+            app.logger.addHandler(mail_handler)
+        else:
+            app.logger.warning(
+                "Mail configuration missing: SMTP error handler not registered!"
+            )