use urllib for URIs

[gigamicro]

fixes percent encoding being broken (eg when steam opens ranger as default file manager)
may break paths that are actually named in percent encoding (that are not themselves percent encoded)
i imagine there's a better way to do this but this seems to work so far

ISSUE TYPE

• Bug fix
• Improvement/feature implementation
• Breaking changes
  (i feel like depending on definition it could be any or all of these)

RUNTIME ENVIRONMENT

• Operating system and version: Linux Lite 5.4
• Terminal emulator and version: alacritty 0.12.2
• Python version: Python 3.8.10
• Ranger version/commit: 136416c
• Locale: en_US.UTF-8

CHECKLIST

• The CONTRIBUTING document has been read [REQUIRED]
• All changes follow the code style [REQUIRED] (at least as far as i can tell after reading it, the import from within a function seems odd but matches the rest of the file afaik)
• All new and existing tests pass [REQUIRED]
• Changes require config files to be updated
  • Config files have been updated
• Changes require documentation to be updated
  • Documentation has been updated
• Changes require tests to be updated
  • Tests have been updated

DESCRIPTION

uses urllib.parse.urlparse and urllib.parse.unquote to, respectively, parse the path from a URI and decode URI percent encoding
potential better way would be to only unquote() the path if it is actually a file:// uri but i literally do not know python

MOTIVATION AND CONTEXT

my previous fix was to make the exo preferred filemanager a shell script that removed the file:// and replaced %20's with spaces before passing any path to ranger (the current apt version of ranger has a bug where it removes the leading slash of file uris, but that was fixed by cloning the repo)

TESTING

"What tests have been run?"
make test_py; make test
"How does the changes affect other areas of the codebase?"
shouldn't, apart from changing the argument parsing