tests: fix cashaddr checksum test unreliability

needs to seed the RNG because there is some low chance of failure.

lib/tests/test_cashaddrenc.py

@@ -25,10 +25,13 @@
 
 import binascii
 import unittest
-import random
+from random import Random
 from .. import cashaddr
 
 
+random = Random()
+
+
 BCH_PREFIX = "bitcoincash"
 BCH_TESTNET_PREFIX = "bchtest"
 
@@ -57,6 +60,10 @@
 class TestCashAddrAddress(unittest.TestCase):
     """Unit test class for cashaddr addressess."""
 
+    def setUp(self):
+        global random
+        random = Random(42)
+
     # Valid address sizes from the cashaddr spec
     valid_sizes = [160, 192, 224, 256, 320, 384, 448, 512]