Allows descriptors to raise Conflict error.

Conflict (HTTP RESPONSE 409) indicates that there is a user-resolvable
problem with the state of the addressed resource.  For Axilent, we're
going to use Conflict to indicate a mis-configured content policy.

sharrock/descriptors.py

@@ -452,3 +452,12 @@ def status_code(self,request):
         """
         return Resource.response_codes[request.method.lower()]
 
+# =======================
+# = Miscellaneous Erros =
+# =======================
+
+class Conflict(Exception):
+    """
+    An exception indicating there is a user-resolvable problem with the function or resource being addressed.
+    Should contain enough information so that the user can resolve the problem.
+    """

sharrock/views.py

@@ -2,7 +2,7 @@
 View functions for Sharrock.
 """
 from sharrock import registry
-from sharrock.descriptors import ParamRequired, MethodNotAllowed, AccessDenied
+from sharrock.descriptors import ParamRequired, MethodNotAllowed, AccessDenied, Conflict
 from django.shortcuts import render_to_response
 from django.http import Http404, HttpResponse
 import traceback
@@ -62,6 +62,8 @@ def execute_service(request,app,version,service_name,extension='json'):
         return HttpResponse(str(ad),status=403)
     except ParamRequired as pr:
         return HttpResponse(str(pr),status=400) # missing parameter
+    except Conflict as con:
+        return HttpResponse(str(con),status=409) # something user-resolvable is wrong with the function
 
 def execute_resource(request,app,version,resource_name,extension='json',model_id=None):
     """
@@ -85,6 +87,8 @@ def execute_resource(request,app,version,resource_name,extension='json',model_id
         return HttpResponse(str(pr),status=400) # there is a missing required parameter
     except MethodNotAllowed as mna:
         return HttpResponse(str(mna),status=405) # the employed http method is not supported
+    except Conflict as con:
+        return HttpResponse(str(cont),status=409) # something user-resolvable is wrong with the resource
     except Exception as e:
         traceback.print_exc()
         raise e