Added a Forbidden exception

Also added a small test.

sanic/exceptions.py

@@ -194,6 +194,11 @@ class ContentRangeError(SanicException):
         }
 
 
+@add_status_code(403)
+class Forbidden(SanicException):
+    pass
+
+
 class InvalidRangeType(ContentRangeError):
     pass
 

tests/test_exceptions.py

@@ -3,7 +3,8 @@ from bs4 import BeautifulSoup
 
 from sanic import Sanic
 from sanic.response import text
-from sanic.exceptions import InvalidUsage, ServerError, NotFound, abort
+from sanic.exceptions import InvalidUsage, ServerError, NotFound, Forbidden
+from sanic.exceptions import abort
 
 
 class SanicExceptionTestException(Exception):
@@ -26,6 +27,10 @@ def exception_app():
     def handler_404(request):
         raise NotFound("OK")
 
+    @app.route('/403')
+    def handler_403(request):
+        raise Forbidden("Forbidden")
+
     @app.route('/invalid')
     def handler_invalid(request):
         raise InvalidUsage("OK")
@@ -91,6 +96,12 @@ def test_not_found_exception(exception_app):
     assert response.status == 404
 
 
+def test_forbidden_exception(exception_app):
+    """Test the built-in Forbidden exception"""
+    request, response = exception_app.test_client.get('/403')
+    assert response.status == 403
+
+
 def test_handled_unhandled_exception(exception_app):
     """Test that an exception not built into sanic is handled"""
     request, response = exception_app.test_client.get('/divide_by_zero')