Created temporary file is not accessable in production

I have written a custom filefield AudioFileField. For this i created a check if a file really is a valid audiofile. To be able to do that, i use the sox commandlinetool, so i have to create a file on disk first. As sox depends on the suffix to do that validation, i needed to write my own TemporaryUploadedAudioFile, using the original suffix (instead of .upload):

class TemporaryUploadedAudioFile(TemporaryUploadedFile):
    """
       A file uploaded to a temporary location (i.e. stream-to-disk).
    """
    def __init__(self, name, content_type, size, charset, suffi开发者_如何学Cx='.upload'):
        """
            The init method overrides the name creation to allow passing
            an extension, so that sox is able to test the file
        """
        if settings.FILE_UPLOAD_TEMP_DIR:
            file = tempfile.NamedTemporaryFile(suffix=suffix,
                dir=settings.FILE_UPLOAD_TEMP_DIR)
        else:
            file = tempfile.NamedTemporaryFile(suffix=suffix)
        super(TemporaryUploadedFile, self).__init__(file, name, content_type, size, charset)  

That file i use to do the audiovalidation in the AudioFileForm to_python method:

def to_python(self, data):
    """
       checks that the file-upload field data contains a valid audio file.
    """
    f = super(AudioFileForm, self).to_python(data)
    if f is None:
        return None

    # get the file suffix, sox needs this to be able to test the file
    suffix = os.path.splitext(data.name)[1]

    # We need to get a temporary file for sox. Even if we allready  have a temporary 
    # file, we have to create a new one ending with the correct suffix
    file = TemporaryUploadedAudioFile(data.name, data.content_type, 0, data.charset,suffix = suffix)
    with open(file.temporary_file_path(), 'w') as f:
        f.write(data.read())

    # Do the validation of the audiofile.
    filetype=subprocess.Popen([sox,'--i','-t','%s'%file.temporary_file_path()], shell=False, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
    filetype=filetype.communicate()[0]
    filetype=filetype.replace('\n','')
    if not filetype in ['wav','aiff','flac']:
        raise forms.ValidationError('Not a valid audiofile (valid are: aif, flac & wav | 16 or 24 bit | 44.1 or 48 kHz)')
    return data  

Now to the strange things happening: this works like a charm on the development server, but as soon as i switch to apache2/mod_wsgi it stops working. sox returns an error telling me that the file is missing.

I have allready checked rights, tmp-location on the production server is /tmp, all rights are granted there (777). What else could be happening here?

mod-wsgi is known to have problems with standard output and this subprocess thingy with django. There are already lot of questions answered about this in stackoverflow.com.

A quick Google search should help you!