web: Add top-level error handler

src/rouse/web/__init__.py

@@ -4,8 +4,13 @@ from milla.dispatch import routing
 import functools
 import jinja2
 import json
+import logging
 import milla.util
 import os
+import sys
+
+
+log = logging.getLogger(__name__)
 
 
 class SmartJSONEncoder(json.JSONEncoder):
@@ -58,6 +63,8 @@ class VariedResponse(milla.Response):
 
 class Application(milla.Application):
 
+    ERROR_TMPL = None
+
     def __init__(self, config=None):  # pylint: disable=super-init-not-called
         self.config = {}
         if config and os.path.exists(config):
@@ -93,3 +100,20 @@ class Application(milla.Application):
             request.want = 'xhtml'
         request.ResponseClass = VariedResponse.for_request(request)
         return request
+
+    def handle_error(self, request):
+        response = request.ResponseClass()
+        e = sys.exc_info()[1]
+        context = {}
+        if isinstance(e, milla.HTTPRedirection):
+            return e
+        elif isinstance(e, milla.WSGIHTTPException):
+            log.debug('{}'.format(e))
+            response.status_int = e.code
+            context['error'] = '{}'.format(e)
+        else:
+            log.exception('An unhandled exception occurred:')
+            response.status_int = 500
+            context['error'] = 'An unknown error has occurred'
+        response.set_payload(self.ERROR_TMPL, context)
+        return response