py3: byteify an inline python test extension

# skip-blame for b'' prefixing

tests/test-largefiles-wireproto.t

@@ -424,12 +424,12 b' a large file from the server rather than'
   > import base64
   > from mercurial.hgweb import common
   > def perform_authentication(hgweb, req, op):
-  >     auth = req.headers.get('Authorization')
+  >     auth = req.headers.get(b'Authorization')
   >     if not auth:
-  >         raise common.ErrorResponse(common.HTTP_UNAUTHORIZED, 'who',
-  >                 [('WWW-Authenticate', 'Basic Realm="mercurial"')])
-  >     if base64.b64decode(auth.split()[1]).split(':', 1) != ['user', 'pass']:
-  >         raise common.ErrorResponse(common.HTTP_FORBIDDEN, 'no')
+  >         raise common.ErrorResponse(common.HTTP_UNAUTHORIZED, b'who',
+  >                 [(b'WWW-Authenticate', b'Basic Realm="mercurial"')])
+  >     if base64.b64decode(auth.split()[1]).split(b':', 1) != [b'user', b'pass']:
+  >         raise common.ErrorResponse(common.HTTP_FORBIDDEN, b'no')
   > def extsetup():
   >     common.permhooks.insert(0, perform_authentication)
   > EOT