Hostname is handled case sensitive which is incorrect

[jmayer]

I recently came along the following url:
http://YouTube.com/watch?v=v0BdJmx-yKg
youtube-dl failed. After writing youtube instead of YouTube it worked. This behaviour is not what would happen in a browser: A browser would just load the url, as (dns-)names are case insensitive per RFC.
youtube-dl isn't respecting that.

[FiloSottile]

Python does not support selective flags, so no hostname-only case-insensitiveness.
What about making all the regexs case-insensitive?
I can't see any issue with that ATM...
@phihag ?

[phihag]

It will be a pain the but to add that for all host names, particularly because in some cases, the rest of the URL may not be case-insensitive. Looking at all our extractors, they all seem to have ASCII-only domains. Therefore, we could do a simple case folding beforehand (and if necessary add the IDN support later). I'm looking into it, but patches are always welcome.