Emit a warning in the other case if the endpoint becomes unreachable

[matprov]

For example protected routes, rate-limited, etc.

Same applies for other requests.

stac-populator/collection_processor.py

Lines 79 to 81 in a578dd6

	r = requests.get(os.path.join(stac_host, "collections", collection_id))
	if r.status_code == 200: