fix(auth): improve network error messages and add retry resilience during token polling

[raymyers]

What changed

Two bugs fixed in the OAuth 2.0 device flow login path, surfaced by a real login failure:

Error: Network error during token polling: Network error: 
Authentication failed: Network error during token polling: Network error: 

Bug 1 — Confusing empty error message (http_client.py)

httpx.RequestError subclasses (e.g. ConnectError) can produce an empty str(e). The previous code did:

raise AuthHttpError(f"Network error: {str(e)}")   # → "Network error: "

Fix: fall back to the exception class name when the string is empty:

error_msg = str(e) or type(e).__name__
raise AuthHttpError(f"Network error: {error_msg}")  # → "Network error: ConnectError"

Bug 2 — Single network blip kills the entire login (device_flow.py)

The polling loop raised immediately on the first AuthHttpError, even though the error could be transient (brief connectivity hiccup, DNS blip, etc.). A 10-minute polling window that fails on the very first attempt is not resilient.

Fix: track consecutive network errors and only raise after max_network_errors (default: 3) consecutive failures. Each failed attempt sleeps for interval seconds before retrying, consistent with the rest of the polling loop.

Commands run

make lint    # all checks passed
uv run pytest -m "not integration" --ignore=tests/snapshots -q
# 1274 passed

Before / After

Before:

Waiting for authentication to complete...
Error: Network error during token polling: Network error: 
Authentication failed: Network error during token polling: Network error: 

After (persistent failure):

Waiting for authentication to complete...
Error: Network error during token polling: Network error: ConnectError
Authentication failed: Network error during token polling: Network error: ConnectError

After (transient failure — now recovers silently):

Waiting for authentication to complete...
✓ Authentication successful!

---

🚀 Try this PR

uvx --python 3.12 git+https://github.com/OpenHands/OpenHands-CLI.git@fix/token-polling-network-error-resilience

[github-actions]

Coverage Report •

File	Stmts	Miss	Cover	Missing
openhands_cli/auth
device_flow.py	101	2	98%	124–125
http_client.py	47	0	100%
TOTAL	6647	933	85%