Add mock for pypy

Author: Talha Malik

jsonschema/tests/test_cli.py

@@ -1,4 +1,10 @@
-from unittest import TestCase, mock
+from unittest import TestCase
+
+try:
+    from unittest import mock
+except ImportError:
+    from mock import mock
+
 import json
 import subprocess
 import sys

tox.ini

@@ -35,6 +35,7 @@ deps =
     perf: pyperf
 
     tests,tests_nongpl,coverage,codecov: -r{toxinidir}/test-requirements.txt
+    pypy: mock
 
     coverage,codecov: coverage
     codecov: codecov