There is no math.gcd in python3.

tasksetgen.py

@@ -45,11 +45,14 @@ def query_yes_no(question, default=None):
         elif 'no'.find(choice) == 0:
             return False
 
+def gcd(a, b):
+    return gcd(b, a % b)
+
 def lcm(a, b):
-    return (a * b) / math.gcd(a, b)
+    return (a * b) / gcd(a, b)
 
 def hyperperiod(tasks):
-    periods = [x.period for task in tasks]
+    periods = [task.period for task in tasks]
     hyperperiod = periods[0]
     for period in periods[1:]:
         hyperperiod = lcm(hyperperiod, period)