Added a Unauthorized exception.

Also added a few tests related to this new exception.

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, Unauthorized
+from sanic.exceptions import abort
 
 
 class SanicExceptionTestException(Exception):
@@ -26,6 +27,20 @@ def exception_app():
     def handler_404(request):
         raise NotFound("OK")
 
+    @app.route('/401/basic')
+    def handler_401_basic(request):
+        raise Unauthorized("Unauthorized", "Basic", "Sanic")
+
+    @app.route('/401/digest')
+    def handler_401_digest(request):
+        challenge = {
+            "qop": "auth, auth-int",
+            "algorithm": "MD5",
+            "nonce": "abcdef",
+            "opaque": "zyxwvu",
+        }
+        raise Unauthorized("Unauthorized", "Digest", "Sanic", challenge)
+
     @app.route('/invalid')
     def handler_invalid(request):
         raise InvalidUsage("OK")
@@ -49,8 +64,10 @@ def exception_app():
 
     return app
 
+
 def test_catch_exception_list():
     app = Sanic('exception_list')
+
     @app.exception([SanicExceptionTestException, NotFound])
     def exception_list(request, exception):
         return text("ok")
@@ -91,6 +108,24 @@ def test_not_found_exception(exception_app):
     assert response.status == 404
 
 
+def test_unauthorized_exception(exception_app):
+    """Test the built-in Unauthorized exception"""
+    request, response = exception_app.test_client.get('/401/basic')
+    assert response.status == 401
+    assert response.headers.get('WWW-Authenticate') is not None
+    assert response.headers.get('WWW-Authenticate') == "Basic realm='Sanic'"
+
+    request, response = exception_app.test_client.get('/401/digest')
+    assert response.status == 401
+    
+    auth_header = response.headers.get('WWW-Authenticate')
+    expected = ("Digest realm='Sanic', qop='auth, auth-int', algorithm='MD5', "
+                "nonce='abcdef', opaque='zyxwvu'")
+    
+    assert auth_header is not None
+    assert auth_header == expected
+
+
 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')