Change error code from 405 to 400 for invalid props to @fields/@attrs

Hi all:

I was working through some tickets on validating property names.  I
noticed that the rest interface does throw an error for an invalid
property in @fields. However it is mapped to a 405 (wrong method)
rather than a 400 (bad request). I have made changes to generate
better error messages for:

   @fields=bad

   @fields=good.bad

which return a 400 error. So we see:

{
    "error": {
        "status": 400,
        "msg": "'Unknown property: status.nam'"
    }
}

and

{
    "error": {
        "status": 400,
        "msg": "'Unknown property: status.nam'"
    }
}

respectively.

This change is confined to rest.py::transitive_props() and is used for
@attr as well.

Since this changes the return code I wonder if I can push it without
bumping the rest version. I figure there are very few users but...

Also a filter like:

   issu3?status.nam=o

returns a 403 forbidden error (User does not have search permission on
"issue.status.nam") not a 400 bad request. I think this needs fixing
too. (This can be handled by adding a call to transitive_props().)

Thoughts?

--
				-- rouilj
John Rouillard
===========================================================================
My employers don't acknowledge my existence much less my opinions.