From 7d391bb2e24f2940c82bf52e4e5ed5a7643f0c5c Mon Sep 17 00:00:00 2001
From: Fabian Neumann <mail@fabianneumann.de>
Date: Tue, 24 Jun 2014 21:34:07 +0200
Subject: [PATCH 1/2] New method `RequestHandler.handle_execution_error`

---
 supercell/requesthandler.py | 30 ++++++++++++++++++++++++++++++
 1 file changed, 30 insertions(+)

diff --git a/supercell/requesthandler.py b/supercell/requesthandler.py
index a6943d8..d9da6bc 100644
--- a/supercell/requesthandler.py
+++ b/supercell/requesthandler.py
@@ -116,6 +116,36 @@ def get_template(self, model):
         '''
         raise NotImplemented
 
+    def handle_execution_error(self, exception):
+        '''Handle execution phase exceptions in a customized way.
+
+        Overwrite this method in subclasses to react to certain
+        exceptions, if the default error handling doesn't fit your
+        needs.
+
+        For example, to output model validation errors in a custom
+        JSON representation::
+
+            def handle_execution_error(self, exception):
+                from schematics.exceptions import BaseError
+                if isinstance(exception, BaseError):
+                    self.set_header('Content-Type', 'application/json')
+                    self.set_status(400)
+                    self.write(json.dumps({
+                        'error': True,
+                        'message': exception.messages,
+                    }))
+                    self.finish()
+                    return
+                raise NotImplementedError
+
+        Note that, if you decide you cannot handle the passed-in
+        exception, you may ``raise NotImplementedError`` at any time and
+        the default error handling will take over.
+
+        '''
+        raise NotImplementedError
+
     def _execute_method(self):
         '''Execute the request.
 

From 8b4e5e77b29042e7a7ff400fc9608ccc823f4ef7 Mon Sep 17 00:00:00 2001
From: Fabian Neumann <mail@fabianneumann.de>
Date: Tue, 24 Jun 2014 21:39:53 +0200
Subject: [PATCH 2/2] Call new `handle_execution_error` before falling back to
 normal error handling.

---
 supercell/requesthandler.py | 14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

diff --git a/supercell/requesthandler.py b/supercell/requesthandler.py
index d9da6bc..574ffcb 100644
--- a/supercell/requesthandler.py
+++ b/supercell/requesthandler.py
@@ -164,11 +164,15 @@ def _execute_method(self):
                         headers['Content-Type'], self)
                     consumer = consumer_class()
                     kwargs['model'] = consumer.consume(self, model)
-                except NoConsumerFound:
-                    # TODO return available consumer types?!
-                    raise HTTPError(406)
-                except StandardError as e:
-                    raise HTTPError(400, reason=unicode(e))
+                except (NoConsumerFound, StandardError) as e:
+                    try:
+                        return self.handle_execution_error(e)
+                    except NotImplementedError:
+                        if isinstance(e, NoConsumerFound):
+                            # TODO return available consumer types?!
+                            raise HTTPError(406)
+                        elif isinstance(e, StandardError):
+                            raise HTTPError(400, reason=unicode(e))
 
             if verb in ['get', 'head']:
                 # check if there is caching information stored with the handler