Handle percent-encoded URLs in parsing code

[paulkeene]

Hi,

Clients of redis-py that attempt to instantiate a ConnectionPool object by using the from_url class method can run into problems if components of the passed-in URL contain illegal characters (e.g. rediss://:my/password@localhost:6379). Understandably the forward slash in this example URL causes it to be parsed incorrectly, but even if a client attempts to percent-encode their URL (e.g. rediss://:my%2Fpassword@localhost:6379) this will not fix the problem since from_url will not know to decode the password after the URL is parsed.

This commit attempts to fix the problem by introducing a new argument, decode_components, to from_url that allows URL components to be decoded after the URL has been parsed. I used a flag here because existing clients might be relying on the current behavior.

I added some unit tests and verified that they pass with python2 and python3.

This fixes issue #579

Thanks,
Paul

[yozik04]

Great. But sad it was not released to pypi yet.