AssertionError: Header values must be strings

[heroku-python]

AssertionError: Header values must be strings

[joshkehn]

New information on the header issue. I dug into the static package and added some debugging lines. The bad headers are generated when unicode strings are added for the Content-Type header as shown below:

10:02:04 web.1  | Exception: [('Date', 'Mon, 03 Mar 2014 15:02:04 -0000'), ('Last-Modified', 'Mon, 03 Mar 2014 14:40:23 -0000'), ('ETag', '1393857623.0'), ('Content-Type', u'text/javascript')]
10:02:04 web.1  | [03/Mar/2014 10:02:04] "GET /static/js/application.min.d96c71a1463c.js HTTP/1.1" 500 59

I cannot trace back where this is coming from. Any other suggestions @kennethreitz?

[lukearno]

Just hearing about this now: lukearno/static#4

Static just uses mimetypes to guess the type, which does not appear to give unicode:

>>> import mimetypes
>>> mimetypes.guess_type('/foo.js')
('application/javascript', None)

I tried it in Python 2.7 and 3.3.

[joshkehn]

I tried that as well and noticed it behaved correctly. There are two sections for guessing the content type:

# Cling
def _guess_type(self, full_path):
    """Guess the mime type using the mimetypes module."""
    return mimetypes.guess_type(full_path)[0] or 'text/plain'

# Shock
def _guess_type(self, full_path):
    """Guess the mime type magically or using the mimetypes module."""
    magic = self._match_magic(full_path)
    if magic is not None:
        return (mimetypes.guess_type(magic.old_path(full_path))[0]
                or 'text/plain')
    else:
        return mimetypes.guess_type(full_path)[0] or 'text/plain'

I'm using Cling (assuming) with a stock implementation:

from django.core.wsgi import get_wsgi_application
from dj_static import Cling
application = Cling(get_wsgi_application())

[lukearno]

Does django-pipeline add mappings to mimetypes?

[joshkehn]

Digging into that I see:

'PIPELINE_MIMETYPES': (
    (b'text/coffeescript', '.coffee'),
    (b'text/less', '.less'),
    (b'application/javascript', '.js'),
    (b'text/x-sass', '.sass'),
    (b'text/x-scss', '.scss')
),

And then again in utils:

def guess_type(path, default=None):
    for type, ext in settings.PIPELINE_MIMETYPES:
        mimetypes.add_type(type, ext)
    mimetype, _ = mimetypes.guess_type(path)
    if not mimetype:
        return default
    return smart_str(mimetype)

I'm not sure how smart_str works or the implication of having binary strings declared in PIPELINE_MIMETYPES.

[lukearno]

I think that's it. Looks like it's fixed in the latest pipeline release (1.3.21).

jazzband/django-pipeline#297
jazzband/django-pipeline@f0b8f72

[joshkehn]

I updated to 1.3.22 and this all appears to be working now. Yay for cross-package contamination of mimetypes..

[joshkehn]

I just discovered an old version of pipeline in a project template and this being the first search result for the error saved me a lot of time. 👍

[gone]

Ditto - 👍