Here is a link to the documentation for namedtuple. You aren't initializing it properly.
How I'm guessing you should initialize it:
cpuInfo = collections.namedtuple('cpuStats', ['usr', 'nice', 'sys', 'idle'])
# In this case, usr=str(currentTime) + " " +str(cpuStats[0]) + " host=" + thisClient
# You can figure the rest out...
info = cpuInfo(usr='fill',
nice='this',
sys='your',
idle='self')
Also, you might want to read this question which talks about serializing namedtuples in json.