Send error mail to admin

Closes: #8

geocode/error_mail.py

@@ -0,0 +1,72 @@
+"""Send mail to admin when an error happens."""
+
+import logging
+from logging import Formatter
+from logging.handlers import SMTPHandler
+
+import flask
+from flask import g, request
+
+PROJECT = "geocode"
+
+
+class MySMTPHandler(SMTPHandler):
+    """Custom SMTP handler to change mail subject."""
+
+    def getSubject(self, record: logging.LogRecord) -> str:
+        """Specify subject line for error mails."""
+        subject = (
+            f"{PROJECT} error: {record.exc_info[0].__name__}"
+            if (record.exc_info and record.exc_info[0])
+            else f"{PROJECT} error: {record.pathname}:{record.lineno:d}"
+        )
+
+        if qid := getattr(g, "qid", None):
+            subject += f" {qid}"
+
+        if label := getattr(g, "label", None):
+            subject += f": {label}"
+
+        return subject
+
+
+class RequestFormatter(Formatter):
+    """Custom logging formatter to include request."""
+
+    def format(self, record: logging.LogRecord) -> str:
+        """Record includes request."""
+        record.request = request
+        return super().format(record)
+
+
+def setup_error_mail(app: flask.Flask) -> None:
+    """Send mail to admins when an error happens."""
+    formatter = RequestFormatter(
+        """
+    Message type:       {levelname}
+    Location:           {pathname:s}:{lineno:d}
+    Module:             {module:s}
+    Function:           {funcName:s}
+    Time:               {asctime:s}
+    GET args:           {request.args!r}
+    URL:                {request.url}
+
+    Message:
+
+    {message:s}
+    """,
+        style="{",
+    )
+
+    mail_handler = MySMTPHandler(
+        app.config["SMTP_HOST"],
+        app.config["MAIL_FROM"],
+        app.config["ADMINS"],
+        app.name + " error",
+        timeout=30,
+    )
+    mail_handler.setFormatter(formatter)
+
+    mail_handler.setLevel(logging.ERROR)
+    app.logger.propagate = True
+    app.logger.addHandler(mail_handler)

lookup.py

@@ -12,11 +12,13 @@ from werkzeug.wrappers import Response
 
 import geocode
 from geocode import database, model, scotland, wikidata
+from geocode.error_mail import setup_error_mail
 
 city_of_london_qid = "Q23311"
 app = Flask(__name__)
 app.config.from_object("config.default")
 database.init_app(app)
+setup_error_mail(app)
 
 Tags = typing.Mapping[str, str]
 logging_enabled = True