feat(python): catch all exceptions thrown through fastapi route paths

This commit does quite a bit:
- Catches unhandled exceptions raised in the route handler and
  produces a 500 Internal Server Error Arch-themed response.
- Each unhandled exception causes a notification to be sent to new
  `notifications.postmaster` email with a "Traceback ID."
- Traceback ID is logged to the server along with the traceback which
  caused the 500: `docker-compose logs fastapi | grep '<traceback_id>'`
- If `options.traceback` is set to `1`, traceback is displayed in
  the new 500.html template.

Signed-off-by: Kevin Morris <kevr@0cost.org>

test/test_asgi.py

@@ -1,19 +1,28 @@
 import http
 import os
+import re
 
 from unittest import mock
 
+import fastapi
 import pytest
 
 from fastapi import HTTPException
+from fastapi.testclient import TestClient
 
 import aurweb.asgi
 import aurweb.config
 import aurweb.redis
 
+from aurweb.testing.email import Email
 from aurweb.testing.requests import Request
 
 
+@pytest.fixture
+def setup(db_test, email_test):
+    return
+
+
 @pytest.mark.asyncio
 async def test_asgi_startup_session_secret_exception(monkeypatch):
     """ Test that we get an IOError on app_startup when we cannot
@@ -66,3 +75,45 @@ async def test_asgi_app_unsupported_backends():
         expr = r"^.*\(sqlite\) is unsupported.*$"
         with pytest.raises(ValueError, match=expr):
             await aurweb.asgi.app_startup()
+
+
+def test_internal_server_error(setup: None,
+                               caplog: pytest.LogCaptureFixture):
+    config_getboolean = aurweb.config.getboolean
+
+    def mock_getboolean(section: str, key: str) -> bool:
+        if section == "options" and key == "traceback":
+            return True
+        return config_getboolean(section, key)
+
+    @aurweb.asgi.app.get("/internal_server_error")
+    async def internal_server_error(request: fastapi.Request):
+        raise ValueError("test exception")
+
+    with mock.patch("aurweb.config.getboolean", side_effect=mock_getboolean):
+        with TestClient(app=aurweb.asgi.app) as request:
+            resp = request.get("/internal_server_error")
+    assert resp.status_code == int(http.HTTPStatus.INTERNAL_SERVER_ERROR)
+
+    # Let's assert that a notification was sent out to the postmaster.
+    assert Email.count() == 1
+
+    aur_location = aurweb.config.get("options", "aur_location")
+    email = Email(1)
+    assert f"Location: {aur_location}" in email.body
+    assert "Traceback ID:" in email.body
+    assert "Version:" in email.body
+    assert "Datetime:" in email.body
+    assert f"[1] {aur_location}" in email.body
+
+    # Assert that the exception got logged with with its traceback id.
+    expr = r"FATAL\[.{7}\]"
+    assert re.search(expr, caplog.text)
+
+    # Let's do it again; no email should be sent the next time,
+    # since the hash is stored in redis.
+    with mock.patch("aurweb.config.getboolean", side_effect=mock_getboolean):
+        with TestClient(app=aurweb.asgi.app) as request:
+            resp = request.get("/internal_server_error")
+    assert resp.status_code == int(http.HTTPStatus.INTERNAL_SERVER_ERROR)
+    assert Email.count() == 1

test/test_auth_routes.py

@@ -1,3 +1,5 @@
+import re
+
 from datetime import datetime
 from http import HTTPStatus
 from unittest import mock
@@ -322,9 +324,13 @@ def test_generate_unique_sid_exhausted(client: TestClient, user: User,
             response = request.post("/login", data=post_data, cookies={})
     assert response.status_code == int(HTTPStatus.INTERNAL_SERVER_ERROR)
 
-    expected = "Unable to generate a unique session ID"
-    assert expected in response.text
     assert "500 - Internal Server Error" in response.text
 
-    # Make sure an IntegrityError from the DB got logged out.
+    # Make sure an IntegrityError from the DB got logged out
+    # with a FATAL traceback ID.
+    expr = r"FATAL\[.{7}\]"
+    assert re.search(expr, caplog.text)
     assert "IntegrityError" in caplog.text
+
+    expr = r"Duplicate entry .+ for key .+SessionID.+"
+    assert re.search(expr, response.text)