XSendFileResponse for Django with fallback when XSendFile is disabled

xsendfile.py

from django.http import HttpResponse
from mimetypes import guess_type
import settings
import re, os

class XSendFileError(Exception):
	pass

class XSendFileResponse(HttpResponse):
	def __init__(self, file_path, content_type=None):
		if not os.path.exists(file_path):
			raise IOError('File does not exist')
		# convert path
		file_path = os.path.realpath(file_path)
		if not content_type:
			content_type = guess_type(file_path)[0]

		try:
			settings.USE_XSENDFILE and settings.XSENDFILE_ROOT
		except AttributeError:
			raise XSendFileError('XSENDFILE_ROOT is required when USE_XSENDFILE is enabled')

		# XSendFile disabled, read the content and pass it to browser
		if not settings.USE_XSENDFILE:
			f = open(file_path, 'r')
			content = f.read()
		else:
			content = ''

		super(XSendFileResponse, self).__init__(content=content, content_type=content_type)

		# add X-Sendfile header if enabled
		if settings.USE_XSENDFILE:
			path = re.sub(r'^' + os.path.realpath(settings.XSENDFILE_ROOT) + r'/?', '', file_path)
			self['X-Sendfile'] = path
		else:
			self['Content-Length'] = os.path.getsize(file_path)