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#!/usr/bin/env python3
# -*- Mode: Python; coding: utf-8; indent-tabs-mode: nil; tab-width: 4 -*-
# Copyright (C) 2022 Authors
#
# Released under GNU GPLv2 or later, read the file 'LICENSE.GPLv2+' for
# more information.
#
# Authors:
# Bryce Harrington <bryce@canonical.com>
"""Utilities for reading input and writing output to external locations."""
import sys
import urllib.request
def open_url(url, desc="data"):
"""Open a remote URL for reading.
:rtype: urllib.request.Request
:returns: A request object for the stream to read from, or None on error.
"""
request = urllib.request.Request(url)
request.add_header('Cache-Control', 'max-age=0')
try:
return urllib.request.urlopen(request)
except urllib.error.HTTPError as e:
if e.code == 401:
# 401 means access denied. Launchpad sometimes returns this
# when something is not published yet.
return None
elif e.code == 404:
# 404 means not found; prefer not to emit error messages
return None
else:
sys.stderr.write(f"Error: Could not retrieve {desc} from {url}: {e}\n")
return None
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