Make sure all errors have a code/reason

Silences some warnings in my editor, and makes sure if it is subclassed
in the future we don't blow up in code somewhere.

waitress/utilities.py

@@ -271,6 +271,9 @@ def cleanup_unix_socket(path):
 
 
 class Error(object):
+    code = 500
+    reason = "Internal Server Error"
+
     def __init__(self, body):
         self.body = body
 
@@ -280,6 +283,7 @@ def to_response(self):
         tag = "\r\n\r\n(generated by waitress)"
         body = body + tag
         headers = [("Content-Type", "text/plain")]
+
         return status, headers, body
 
     def wsgi_response(self, environ, start_response):