Session.get_adapter won't work correctly for case-sensitive URLs

In its current implementation Session.get_adapter turns url to lowercase in line 637. If it is aiming for case-insensitive compare it should also turn prefix variable to lowercase in the same line or do that at registration in the mount() method. But this whole idea seems incorrect because URL paths can be case sensitive and one might register different adapters for different paths on the same site.

The fix should most likely be spliting the URL into components and using that tuple as a key in the self.adapters dictionary. Changes mount() and get_adapter().

In [48]: urlparse.urlparse('HTTP://lala.mi.do/path')
Out[48]: ParseResult(scheme='http', netloc='lala.mi.do', path='/path', params='', query='', fragment='')

In [49]: d = {}

In [50]: purl = urlparse.urlparse('HTTP://lala.mi.do/path')

In [51]: d[purl] = 'myadapter'

In [52]: purl = urlparse.urlparse('HTTP://lala.mi.do/Path2')

In [53]: purl
Out[53]: ParseResult(scheme='http', netloc='lala.mi.do', path='/Path2', params='', query='', fragment='')

In [54]: d[purl] = 'myadapter2'

In [55]: d
Out[55]:
{ParseResult(scheme='http', netloc='lala.mi.do', path='/Path2', params='', query='', fragment=''): 'myadapter2',
 ParseResult(scheme='http', netloc='lala.mi.do', path='/path', params='', query='', fragment=''): 'myadapter'}

Start with Session.get_adapter around line 637 and the mount() method, then inspect how self.adapters stores prefixes and how urlparse represents URL components. Reproduce the two case-sensitive paths described in the issue and trace adapter selection. Done means scheme and host matching remain appropriate while distinct path casing can select different registered adapters.