web: `UnicodeEncodeError` on non-latin1 characters in filename

[UniIsland]

Problem

I'm using beet with tomahawk. If I try to play a song with CJK character in its name, the web server throws UnicodeEncodeError.

127.0.0.1 - - [22/Feb/2018 15:28:19] "GET /item/10933/file HTTP/1.0" 200 -
Error on request:
Traceback (most recent call last):
  File "/usr/local/Cellar/pyenv/1.2.1/versions/3.6.4/lib/python3.6/site-packages/werkzeug/serving.py", line 270, in run_wsgi
    execute(self.server.app)
  File "/usr/local/Cellar/pyenv/1.2.1/versions/3.6.4/lib/python3.6/site-packages/werkzeug/serving.py", line 261, in execute
    write(data)
  File "/usr/local/Cellar/pyenv/1.2.1/versions/3.6.4/lib/python3.6/site-packages/werkzeug/serving.py", line 227, in write
    self.send_header(key, value)
  File "/usr/local/Cellar/pyenv/1.2.1/versions/3.6.4/lib/python3.6/http/server.py", line 508, in send_header
    ("%s: %s\r\n" % (keyword, value)).encode('latin-1', 'strict'))
UnicodeEncodeError: 'latin-1' codec can't encode characters in position 46-50: ordinal not in range(256)

Here's a song that can cause this problem (fields dumped with the export plugin):

  {
        "acoustid_fingerprint": null,
        "acoustid_id": null,
        "album": "匆匆",
        "albumartist": "胡德夫",
        "albumartist_credit": "胡德夫",
        "albumartist_sort": "Ara Kimbo",
        "albumdisambig": null,
        "albumstatus": "Official",
        "albumtype": "album",
        "arranger": "",
        "art": false,
        "artist": "胡德夫",
        "artist_credit": "胡德夫",
        "artist_sort": "Ara Kimbo",
        "asin": null,
        "bitdepth": 0,
        "bitrate": 128000,
        "bpm": 0,
        "catalognum": "WFM05001",
        "channels": 2,
        "comments": null,
        "comp": false,
        "composer": null,
        "composer_sort": null,
        "country": "TW",
        "date": "2005-04-01",
        "day": null,
        "disc": 1,
        "disctitle": null,
        "disctotal": 1,
        "encoder": null,
        "format": "MP3",
        "genre": "Folk",
        "genres": [
            "Folk"
        ],
        "grouping": null,
        "initial_key": null,
        "label": "野火樂集",
        "language": "zho",
        "length": 316.6040625,
        "lyricist": null,
        "lyrics": "",
        "mb_albumartistid": "46dfef42-826d-4cb1-8d28-940d30aa3bf9",
        "mb_albumid": "de95a0cb-87c0-4d64-b753-f5c98bde3271",
        "mb_artistid": "46dfef42-826d-4cb1-8d28-940d30aa3bf9",
        "mb_releasegroupid": "0fe19e52-b54b-4a6a-946d-a23b58766e7c",
        "mb_trackid": "b69fce9c-373b-46a3-b060-4ffdc4800430",
        "media": "CD",
        "month": 4,
        "original_date": "2005-04-01",
        "original_day": null,
        "original_month": 4,
        "original_year": 2005,
        "r128_album_gain": 0,
        "r128_track_gain": 0,
        "rg_album_gain": -4.44,
        "rg_album_peak": 1.088344,
        "rg_track_gain": -5.09,
        "rg_track_peak": 1.032934,
        "samplerate": 44100,
        "script": "Hant",
        "title": "太平洋的風",
        "track": 1,
        "tracktotal": 12,
        "year": 2005
    }

Setup

• OS: MacOS 10.13.3
• Python version: 3.6.4
• beets version: 1.4.6

[sampsyo]

Hello! Thanks for the details. Because this error happens when sending the headers, I suspect that the problem only occurs because there are non-Latin1 characters in the filename (not just in the metadata). Can you confirm that the filename has CJK characters?

[waweic]

This seems like a Python 3 specific issue. It works fine for me with Python 2.7 and Chromium. In Python 3, it even occurs on characters like single right quotation marks (u2019), that can be found in filenames pretty often. This could possibly be prevented by "de-asciifying" the attachment_filename or taking a fallback filename. Is that an option?

[sampsyo]

Thanks! Yeah, it seems like the right thing to do is to ASCIIfy the filename. (For clues about how to do this, see the uses of unidecode elsewhere in the codebase.)