It's not a bug. Please read the documentation of the split() method:
   http://docs.python.org/library/stdtypes.html#str.split

If you want to get the value after "=", use:
   value = line.split("FILE=", 1)[1]
or:
   value = line[len('FILE='):]
or:
   value = line.partition('FILE=')[2]
or:
   etc.