Add check that user can view feature before sending change notification email

[yanndago]

Changes on features that become confidential should not be sent to users that cannot see them

[jrobbins]

This caused the notification generation task to fail with an exception.
It looks like maybe triggering_user_email is None:

Starting to notify subscribers for feature {'id': 6341838249394176, 'name': 'enterprise with screenshots', 'summary': 'this is where screenshots go to hide and seek in the open', 'blink_components': ['Enterprise'], 'star_count': 1, 'search_tags': [], 'created': {'by': '[email protected]', 'when': '2024-12-12 20:39:24.363234'}, 'updated': {'by': '[email protected]', 'when': '2025-01-10 01:09:05.583087'}, 'category': 'Miscellaneous', 'category_int': 2, 'feature_notes': None, 'web_feature': None, 'enterprise_feature_categories': [], 'enterprise_product_category': 0, 'stages': [{'id': 5921145998278656, 'created': '2024-12-12 20:39:24.549777', 'feature_id': 6341838249394176, 'stage_type': 1061, 'display_name': None, 'intent_stage': 10, 'pm_emails': [], 'tl_emails': [], 'ux_emails': [], 'te_emails': [], 'intent_thread_url': None, 'announcement_url': None, 'experiment_goals': None, 'experiment_risks': None, 'origin_trial_id': None, 'origin_trial_feedback_url': None, 'ot_action_requested': False, 'ot_approval_buganizer_component': None, 'ot_approval_buganizer_custom_field_id': None, 'ot_approval_criteria_url': None, 'ot_approval_group_email': None, 'ot_chromium_trial_name': None, 'ot_description': None, 'ot_display_name': None, 'ot_documentation_url': None, 'ot_emails': [], 'ot_feedback_submission_url': None, 'ot_has_third_party_support': False, 'ot_is_critical_trial': False, 'ot_is_deprecation_trial': False, 'ot_owner_email': None, 'ot_require_approvals': False, 'ot_use_counter_bucket_number': None, 'ot_webfeature_use_counter': None, 'extensions': [], 'experiment_extension_reason': None, 'ot_stage_id': None, 'finch_url': None, 'rollout_milestone': 133, 'rollout_platforms': ['1', '3'], 'rollout_details': None, 'rollout_impact': 2, 'enterprise_policies': [], 'desktop_first': None, 'android_first': None, 'ios_first': None, 'webview_first': None, 'desktop_last': None, 'android_last': None, 'ios_last': None, 'webview_last': None}], 'accurate_as_of': '2024-12-12 20:39:24.362600', 'creator_email': '[email protected]', 'updater_email': '[email protected]', 'owner_emails': ['[email protected]'], 'editor_emails': [], 'cc_emails': [], 'spec_mentor_emails': [], 'unlisted': False, 'deleted': False, 'editors': [], 'cc_recipients': [], 'spec_mentors': [], 'creator': '[email protected]', 'feature_type': 'New Feature or removal affecting enterprises', 'feature_type_int': 4, 'intent_stage': 'None', 'intent_stage_int': 0, 'active_stage_id': None, 'bug_url': None, 'launch_bug_url': None, 'new_crbug_url': 'https://bugs.chromium.org/p/chromium/issues/entry?components=Enterprise&[email protected]', 'screenshot_links': ['https://img640-dot-cr-status-staging.appspot.com/feature/6341838249394176/attachment/5674880646512640'], 'first_enterprise_notification_milestone': 135, 'enterprise_impact': 2, 'breaking_change': False, 'confidential': True, 'shipping_year': None, 'flag_name': None, 'finch_name': None, 'non_finch_justification': None, 'ongoing_constraints': None, 'motivation': None, 'devtrial_instructions': None, 'activation_risks': None, 'measurement': None, 'availability_expectation': None, 'adoption_expectation': None, 'adoption_plan': None, 'initial_public_proposal_url': None, 'explainer_links': [], 'requires_embedder_support': False, 'spec_link': None, 'api_spec': False, 'interop_compat_risks': None, 'all_platforms': None, 'all_platforms_descr': None, 'non_oss_deps': None, 'anticipated_spec_changes': None, 'security_risks': None, 'ergonomics_risks': None, 'wpt': None, 'wpt_descr': None, 'webview_risks': None, 'devrel_emails': [], 'debuggability': None, 'doc_links': [], 'sample_links': [], 'prefixed': None, 'tags': [], 'tag_review': None, 'tag_review_status': 'Not applicable', 'tag_review_status_int': 4, 'security_review_status': 'Pending', 'security_review_status_int': 1, 'privacy_review_status': 'Pending', 'privacy_review_status_int': 1, 'updated_display': None, 'resources': {'samples': [], 'docs': []}, 'comments': None, 'ff_views': 5, 'safari_views': 5, 'web_dev_views': 4, 'browsers': {'chrome': {'bug': None, 'blink_components': ['Enterprise'], 'devrel': [], 'owners': ['[email protected]'], 'origintrial': False, 'intervention': False, 'prefixed': None, 'flag': False, 'status': {'text': 'No active development', 'val': 1, 'milestone_str': 'No active development'}, 'desktop': None, 'android': None, 'webview': None, 'ios': None}, 'ff': {'view': {'url': None, 'notes': None, 'text': 'No signal', 'val': 5}}, 'safari': {'view': {'url': None, 'notes': None, 'text': 'No signal', 'val': 5}}, 'webdev': {'view': {'text': 'No signals', 'val': 4, 'url': None, 'notes': None}}, 'other': {'view': {'text': None, 'val': None, 'url': None, 'notes': None}}}, 'standards': {'spec': None, 'maturity': {'text': None, 'short_text': 'Unknown status', 'val': 0}}, 'is_released': False, 'is_enterprise_feature': True, 'experiment_timeline': None}

Exception on /tasks/email-subscribers [POST]
Traceback (most recent call last):
  File "/layers/google.python.pip/pip/lib/python3.11/site-packages/flask/app.py", line 2190, in wsgi_app
    response = self.full_dispatch_request()
               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/layers/google.python.pip/pip/lib/python3.11/site-packages/flask/app.py", line 1486, in full_dispatch_request
    rv = self.handle_user_exception(e)
         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/layers/google.python.pip/pip/lib/python3.11/site-packages/flask_cors/extension.py", line 194, in wrapped_function
    return cors_after_request(app.make_response(f(*args, **kwargs)))
                                                ^^^^^^^^^^^^^^^^^^
  File "/layers/google.python.pip/pip/lib/python3.11/site-packages/flask/app.py", line 1484, in full_dispatch_request
    rv = self.dispatch_request()
         ^^^^^^^^^^^^^^^^^^^^^^^
  File "/layers/google.python.pip/pip/lib/python3.11/site-packages/flask/app.py", line 1469, in dispatch_request
    return self.ensure_sync(self.view_functions[rule.endpoint])(**view_args)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/layers/google.python.pip/pip/lib/python3.11/site-packages/flask/views.py", line 109, in view
    return current_app.ensure_sync(self.dispatch_request)(**kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/layers/google.python.pip/pip/lib/python3.11/site-packages/flask/views.py", line 190, in dispatch_request
    return current_app.ensure_sync(meth)(**kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/srv/framework/basehandlers.py", line 575, in post
    handler_data = self.process_post_data(*args, **kwargs)
                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/srv/internals/notifier.py", line 458, in process_post_data
    can_view_feature = permissions.can_view_feature(user, fe)
                       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/srv/framework/permissions.py", line 80, in can_view_feature
    return not feature.confidential or _can_view_confidential_feature(user, feature)
                                       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/srv/framework/permissions.py", line 90, in _can_view_confidential_feature
    if is_google_or_chromium_account(user) or can_admin_site(user):
       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/srv/framework/permissions.py", line 44, in is_google_or_chromium_account
    return user.email().endswith(('@chromium.org', '@google.com'))
           ^^^^^^^^^^^^^^^^^^^^^
AttributeError: 'NoneType' object has no attribute 'endswith'

But, also, the triggering user is the person who made the edit to the feature. That user should always have permission to view the feature. I think what you want to check is the permission for the person being notified. That would need to be done in a different function:
https://github.com/GoogleChrome/chromium-dashboard/blob/main/internals/notifier.py#L277