Null vs None check for native python code

[Jim Morrison]

Hi,

  I tried to use mesos-submit from the top of the git tree, unfortunately, I 
got an error about the wrong number of arguments.  When I put None in for the 
missing argument I discovered that the native C code is checking for value != 
null instead of value != PyNone when the value is parsed with Parse_Tuple "O".  
Anyway, attached is a patch that allows me to run the script.

Unfortunately the script hangs when I do:
$ ./frameworks/mesos-submit/mesos-submit MYMASTER:5050 "echo hello world"

All I get is:
Connecting to mesos master MYMASTER:5050 .


Jim