Synnefo

When sharing a file, if a user provides a uuid that has length greater than 257 characters, the server returns 500 Internal Server Error.
A check should be done on the length of any user input.

How to reproduce:

kamaki file permissions set pithos:test.txt read="aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa" 

........

< 500 INTERNAL SERVER ERROR
<   content-length: 84
<   content-language: en-us
<   expires: Tue, 22 Oct 2013 11:34:57 GMT
<   vary: X-Auth-Token,Accept-Language,Accept-Encoding
<   server: gunicorn/0.14.5
<   last-modified: Tue, 22 Oct 2013 11:34:57 GMT
<   connection: close
<   cache-control: no-cache, no-store, must-revalidate, max-age=0
<   date: Tue, 22 Oct 2013 11:34:57 GMT
<   content-type: application/json; charset=UTF-8
< data size: 84
> {"internalServerError": {"message": "Unexpected error", "code": 500, "details": ""}}