External Python packages interfacing beets may want to use an in-memory
beets library instance for testing beets-related code.
The `TestHelper` class is very helpful for this purpose.
Previously `TestHelper` was located in the `test/` directory.
Now it is part of `beets` itself (`beets.test.helper.TestHelper`) and
can be easily imported.
- M3UFile.read() method reads in rb mode.
- M3UFile.read() method handles removal of (platform specific) line endings.
- Playlist contents and EXTM3U header is handled as bytes.
- Fix test_playlist*read* tests to encode playlist UTF-8 assert strings to
bytes using bytestring_path() before comparision.
- Fixture playlist_windows.m3u8 is now actually Windows formatted (\r\n + BOM)
Make sure we stay with the beets standard of handling everything internally as
bytes.
- M3UFile.write() method writes in wb mode.
- Playlist contents and EXTM3U header is handled as bytes.
- item.destination() gives us unicode string paths, we tranlate to bytes
using util.bytestring_path().
- Fix test_playlist*write* tests to encode UTF-8 assert strings as bytes using
bytestring_path() before comparision.
Add test_playlist_write_and_read_unicode_windows: Writes 2 media file
paths containing unicode characters, reads them in using M3UFile class
again and tests if the contents is correct.
- Add and Exception class called EmptyPlaylistError ought to be raised
when playlists without files are loaded or saved.
- Add a test for it in test_m3ufile
- Fix media_files vs. media_list attribute name.
