mock 1.1 breaking py26 job

http://logs.openstack.org/09/202009/1/check/gate-sqlalchemy-migrate-python26/eea82d4/console.html

2015-07-15 14:15:56.204 | running testr
2015-07-15 14:15:56.204 | Traceback (most recent call last):
2015-07-15 14:15:56.204 | File "setup.py", line 21, in <module>
2015-07-15 14:15:56.205 | pbr=True)
2015-07-15 14:15:56.205 | File "/usr/lib64/python2.6/distutils/core.py", line 152, in setup
2015-07-15 14:15:56.205 | dist.run_commands()
2015-07-15 14:15:56.205 | File "/usr/lib64/python2.6/distutils/dist.py", line 975, in run_commands
2015-07-15 14:15:56.206 | self.run_command(cmd)
2015-07-15 14:15:56.206 | File "/usr/lib64/python2.6/distutils/dist.py", line 995, in run_command
2015-07-15 14:15:56.206 | cmd_obj.run()
2015-07-15 14:15:56.207 | File "/home/jenkins/workspace/gate-sqlalchemy-migrate-python26/.tox/py26/lib/python2.6/site-packages/testrepository/setuptools_command.py", line 75, in run
2015-07-15 14:15:56.207 | testr_ret = self._run_testr("run", "--parallel", *self.testr_args)
2015-07-15 14:15:56.207 | File "/home/jenkins/workspace/gate-sqlalchemy-migrate-python26/.tox/py26/lib/python2.6/site-packages/testrepository/setuptools_command.py", line 52, in _run_testr
2015-07-15 14:15:56.208 | sys.stdin, sys.stdout, sys.stderr)
2015-07-15 14:15:56.208 | File "/home/jenkins/workspace/gate-sqlalchemy-migrate-python26/.tox/py26/lib/python2.6/site-packages/testrepository/commands/__init__.py", line 184, in run_argv
2015-07-15 14:15:56.209 | cmdclass = _find_command(cmd_name)
2015-07-15 14:15:56.209 | File "/home/jenkins/workspace/gate-sqlalchemy-migrate-python26/.tox/py26/lib/python2.6/site-packages/testrepository/commands/__init__.py", line 51, in _find_command
2015-07-15 14:15:56.209 | _temp = __import__(modname, globals(), locals(), [classname])
2015-07-15 14:15:56.209 | File "/home/jenkins/workspace/gate-sqlalchemy-migrate-python26/.tox/py26/lib/python2.6/site-packages/testrepository/commands/run.py", line 34, in <module>
2015-07-15 14:15:56.210 | from testrepository.commands.load import load
2015-07-15 14:15:56.210 | File "/home/jenkins/workspace/gate-sqlalchemy-migrate-python26/.tox/py26/lib/python2.6/site-packages/testrepository/commands/load.py", line 31, in <module>
2015-07-15 14:15:56.210 | from testrepository.testcommand import TestCommand
2015-07-15 14:15:56.211 | File "/home/jenkins/workspace/gate-sqlalchemy-migrate-python26/.tox/py26/lib/python2.6/site-packages/testrepository/testcommand.py", line 35, in <module>
2015-07-15 14:15:56.211 | from fixtures import Fixture
2015-07-15 14:15:56.211 | File "/home/jenkins/workspace/gate-sqlalchemy-migrate-python26/.tox/py26/lib/python2.6/site-packages/fixtures/__init__.py", line 87, in <module>
2015-07-15 14:15:56.212 | from fixtures._fixtures import (
2015-07-15 14:15:56.212 | File "/home/jenkins/workspace/gate-sqlalchemy-migrate-python26/.tox/py26/lib/python2.6/site-packages/fixtures/_fixtures/__init__.py", line 55, in <module>
2015-07-15 14:15:56.212 | from fixtures._fixtures.mockpatch import (
2015-07-15 14:15:56.213 | File "/home/jenkins/workspace/gate-sqlalchemy-migrate-python26/.tox/py26/lib/python2.6/site-packages/fixtures/_fixtures/mockpatch.py", line 22, in <module>
2015-07-15 14:15:56.213 | mock = extras.try_imports(['unittest.mock', 'mock'], None)
2015-07-15 14:15:56.213 | File "/home/jenkins/workspace/gate-sqlalchemy-migrate-python26/.tox/py26/lib/python2.6/site-packages/extras/__init__.py", line 87, in try_imports
2015-07-15 14:15:56.214 | module = try_import(module_name, error_callback=error_callback)
2015-07-15 14:15:56.214 | File "/home/jenkins/workspace/gate-sqlalchemy-migrate-python26/.tox/py26/lib/python2.6/site-packages/extras/__init__.py", line 46, in try_import
2015-07-15 14:15:56.214 | module = __import__(module_name)
2015-07-15 14:15:56.215 | File "/home/jenkins/workspace/gate-sqlalchemy-migrate-python26/.tox/py26/lib/python2.6/site-packages/mock/__init__.py", line 2, in <module>
2015-07-15 14:15:56.215 | import mock.mock as _mock
2015-07-15 14:15:56.216 | File "/home/jenkins/workspace/gate-sqlalchemy-migrate-python26/.tox/py26/lib/python2.6/site-packages/mock/mock.py", line 132
2015-07-15 14:15:56.216 | _builtins = {name for name in dir(builtins) if not name.startswith('_')}
2015-07-15 14:15:56.238 | ^
2015-07-15 14:15:56.238 | SyntaxError: invalid syntax
2015-07-15 14:15:56.239 | The test run didn't actually run any tests

We have to update requirements to avoid mock 1.1 on py26.