Fix for https://github.com/andymccurdy/redis-py/issues/1135

[aachurin]

Fix for #1135

Pull Request check-list

Please make sure to review and check all of these items:

• Does $ python setup.py test pass with this change (including linting)?
• Does travis tests pass with this change (enable it first in your forked repo and wait for the travis build to finish)?
• Is the new or changed code fully tested?
• Is a documentation update included (if this change modifies existing APIs, or introduces new ones)?

NOTE: these things are not required to open a PR and can be done
afterwards / while the PR is open.

Description of change

Please provide a description of the change here.

[andymccurdy]

Thanks!