Violated LSP in BlockingConnectionPool makes it impossible to inherit from it

[vladvildanov]

Version: What redis-py and what redis version is the issue happening on?
All

Platform: What platform / version? (For example Python 3.5.1 on Windows 7 / Ubuntu 15.10 / Azure)
All

Description: Description of your issue, stack traces from errors and code that reproduces the issue

LSP is violated inside of BlockingConnectionPool class, so disconnect() method implementation in it cannot substitute the implementation in super class, as arguments set (and behaviour) missmatches. It makes the class non-inheritable (f.e to implement SentinelBlockingConnectionPool), because of the interface changes