Get proxies from os.environ.

def get_proxies_from_environ():
    """Get proxies from os.environ."""
    proxies = {}
    http_proxy = os.getenv('http_proxy') or os.getenv('HTTP_PROXY')
    https_proxy = os.getenv('https_proxy') or os.getenv('HTTPS_PROXY')
    if http_proxy:
        proxies['http'] = http_proxy
    if https_proxy:
        proxies['https'] = https_proxy
    return proxies