Handle errors

TODO: TESTING config setting isn't applying as expected

docker-compose.dev.yml

@@ -21,10 +21,10 @@ services:
       - "USAON_VTA_LOGIN_DISABLED=true"
       # Use a local file DB instead of a remote one:
       - "USAON_VTA_DB_SQLITE=true"
+      # Disable error handlers and allow exceptions to propagate:
+      - "USAON_VTA_TESTING=True"
       # Enable the in-browser debugger:
       - "FLASK_DEBUG=True"
-      # Disable error handlers and allow exceptions to propagate:
-      - "FLASK_TESTING=True"
 
 
       # Development DANGER ZONE: Do not use the below settings except for

usaon_vta_survey/__init__.py

@@ -1,7 +1,7 @@
 import os
 from typing import Final
 
-from flask import Flask
+from flask import Flask, render_template
 from flask_bootstrap import Bootstrap5
 from flask_sqlalchemy import SQLAlchemy
 from sqlalchemy import MetaData
@@ -28,13 +28,28 @@
 app = Flask(__name__)
 app.config['SECRET_KEY'] = os.environ.get('FLASK_SECRET_KEY', 'youcanneverguess')
 app.config['LOGIN_DISABLED'] = envvar_is_true("USAON_VTA_LOGIN_DISABLED")
+# TODO: This should disable error handlers but it doesn't:
+app.config['TESTING'] = envvar_is_true("USAON_VTA_TESTING")
 app.config['SQLALCHEMY_DATABASE_URI'] = db_connstr(app)
 
 db.init_app(app)
 bootstrap = Bootstrap5(app)
 
 app.jinja_env.globals.update(sqla_inspect=sqla_inspect, __version__=__version__)
 
+
+@app.errorhandler(Exception)
+def handle_exception(e):
+    """Naively handle all exceptions the same way.
+
+    TODO: Not all exceptions should necessarily be handled the same way. Think harder.
+          Read docs: https://flask.palletsprojects.com/en/2.3.x/errorhandling/
+    TODO: Some way to link error messages users see with full tracebacks in logs. A
+          random request ID?
+    """
+    return render_template("error.html", message=e)
+
+
 # NOTE: This is a circular import, but it's specified by the Flask docs:
 #     https://flask.palletsprojects.com/en/3.1.x/patterns/packages/
 import usaon_vta_survey.routes  # noqa: E402, F401