aio-libs/aiohttp · warning · LookupError

No .netrc file found

Error message

No .netrc file found

What it means

Raised by _auth_header_from_netrc when netrc_obj is None, i.e. no usable .netrc file was loaded (missing, unreadable, or unparseable). It is a LookupError, surfaced when the client tries to derive Proxy-Authorization from netrc for a proxy host.

Source

Thrown at aiohttp/helpers.py:243

            client_logger.warning("Could not read .netrc file: %s", e)

    return None


@frozen_dataclass_decorator
class ProxyInfo:
    proxy: URL
    proxy_auth: str | None


def _auth_header_from_netrc(netrc_obj: netrc.netrc | None, host: str) -> str:
    """Return a ``Proxy-Authorization`` header value for ``host`` from netrc.

    :raises LookupError: if ``netrc_obj`` is :py:data:`None` or if no
            entry is found for the ``host``.
    """
    if netrc_obj is None:
        raise LookupError("No .netrc file found")
    auth_from_netrc = netrc_obj.authenticators(host)

    if auth_from_netrc is None:
        raise LookupError(f"No entry for {host!s} found in the `.netrc` file.")
    login, account, password = auth_from_netrc

    # TODO(PY311): username = login or account
    # Up to python 3.10, account could be None if not specified,
    # and login will be empty string if not specified. From 3.11,
    # login and account will be empty string if not specified.
    username = login if (login or account is None) else account

    # TODO(PY311): Remove this, as password will be empty string
    # if not specified
    if password is None:
        password = ""  # type: ignore[unreachable]

    return encode_basic_auth(username, password)

View on GitHub (pinned to c0ef574e29)

Solutions

1. Create a valid ~/.netrc (chmod 600) with a 'machine <proxyhost>' entry.
2. Set NETRC env var to an absolute readable file path.
3. Pass proxy auth explicitly via the proxy URL or trust_env=False with explicit connector config.

Example fix

// before
# no .netrc, trust_env=True, proxy requires auth
// after
# chmod 600 ~/.netrc with: machine proxy.local login me password xxx

from pathlib import Path
import os
netrc_path = Path(os.environ.get('NETRC') or (Path.home() / '.netrc'))
if not netrc_path.is_file():
    raise FileNotFoundError(f'configure {netrc_path}')

try:
    auth = _auth_header_from_netrc(netrc_obj, host)
except LookupError:
    auth = None  # fall back to no netrc auth

When it happens

Trigger: Trust env enabled with a proxy URL whose host has no credentials, while no .netrc exists at $NETRC or in the home directory. The lookup is invoked from proxies_from_env when proxy auth is needed and not in the URL.

Common situations: CI/container environments without HOME or .netrc; misconfigured NETRC env var pointing to a non-existent path; permissions blocking the file.

Related errors

• No entry for {host!s} found in the `.netrc` file.
• Proxying is disallowed for `{url.host!r}`
• No proxies found for `{url!s}` in the env
• Invalid upgrade header
• Invalid connection header

AI-assisted analysis of aio-libs/aiohttp@c0ef574e29 (2026-08-04). Data as JSON: /data/errors/9993a027e5f2c840.json. Report an issue: GitHub.