Add a BadRequest resource to help with BAD REQUEST

src/allmydata/web/common.py

@@ -21,7 +21,8 @@ from allmydata.util.encodingutil import to_bytes, quote_output
 
 # Originally part of this module, so still part of its API:
 from .common_py3 import (  # noqa: F401
-    get_arg, abbreviate_time, MultiFormatResource, WebError
+    get_arg, abbreviate_time, MultiFormatResource, WebError,
+    BadRequest,
 )
 
 

src/allmydata/web/common_py3.py

@@ -23,6 +23,15 @@ class WebError(Exception):
         self.code = code
 
 
+class BadRequest(resource.ErrorPage):
+    """
+    ``BadRequest`` is a specialiation of ``ErrorPage`` which returns the HTTP
+    response code **BAD REQUEST**.
+    """
+    def __init__(self, message=""):
+        resource.ErrorPage.__init__(self, http.BAD_REQUEST, "Bad Request", message)
+
+
 def get_arg(ctx_or_req, argname, default=None, multiple=False):
     """Extract an argument from either the query args (req.args) or the form
     body fields (req.fields). If multiple=False, this returns a single value