THRIFT-3515 Python 2.6 compatibility and test on CI

This closes #766
diff --git a/test/py/SerializationTest.py b/test/py/SerializationTest.py
index 99e0393..d4755cf 100755
--- a/test/py/SerializationTest.py
+++ b/test/py/SerializationTest.py
@@ -24,6 +24,7 @@
 from thrift.transport import TTransport
 from thrift.protocol import TBinaryProtocol, TCompactProtocol, TJSONProtocol
 from thrift.TSerialization import serialize, deserialize
+import sys
 import unittest
 
 
@@ -258,6 +259,9 @@
     self.assertTrue(len(rep) > 0)
 
   def testIntegerLimits(self):
+    if (sys.version_info[0] == 2 and sys.version_info[1] <= 6):
+      print('Skipping testIntegerLimits for Python 2.6')
+      return
     bad_values = [CompactProtoTestStruct(a_byte=128), CompactProtoTestStruct(a_byte=-129),
                   CompactProtoTestStruct(a_i16=32768), CompactProtoTestStruct(a_i16=-32769),
                   CompactProtoTestStruct(a_i32=2147483648), CompactProtoTestStruct(a_i32=-2147483649),