tests: Drop use of random2

We can use stdlib random module and manually adjust randint to behave
exactly as before Python3, so that testdata are matched exactly as before.

Also drop unnecessary `random.seed(42)` in cache_run. It is not needed
there because random is not used in cache_run at all.

Based on work of @d-maurer in https://github.com/zopefoundation/ZEO/pull/195 .

setup.py

@@ -36,7 +36,6 @@ tests_require = [
     'ZopeUndo',
     'zope.testing',
     'manuel',
-    'random2',
     'transaction',
     'mock',
     'msgpack < 1',

src/ZEO/tests/test_cache.py

@@ -482,8 +482,11 @@ Check to make sure the cache analysis scripts work.
     >>> time.time = lambda : now
 
     >>> os.environ["ZEO_CACHE_TRACE"] = 'yes'
-    >>> import random2 as random
+    >>> import random
     >>> random = random.Random(42)
+    >>> # adjust randint to provide the same output as before Python3 to match
+    >>> # test data. https://stackoverflow.com/a/55800424/9456786
+    >>> random.randint = lambda a, b: a + int(random.random() * (b-a+1))
     >>> history = []
     >>> serial = 1
     >>> for i in range(1000):
@@ -498,7 +501,6 @@ Check to make sure the cache analysis scripts work.
 
     >>> def cache_run(name, size):
     ...     serial = 1
-    ...     random.seed(42)
     ...     global now
     ...     now = 1278864701.5
     ...     cache = ZEO.cache.ClientCache(name, size*(1<<20))