fix up import style

Lib/test/test_float.py

 
-import unittest, struct
+import fractions
+import math
+import operator
 import os
+import random
 import sys
+import struct
+import time
+import unittest
+
 from test import support
-import math
 from math import isinf, isnan, copysign, ldexp
-import operator
-import time
-import random, fractions
 
 INF = float("inf")
 NAN = float("nan")