f Add comment regarding why we retry subscribing

Author: tnull

lightning-transaction-sync/tests/integration_tests.rs

@@ -67,6 +67,9 @@ fn wait_for_block(min_height: usize) {
 	let mut header = match get_electrsd().client.block_headers_subscribe() {
 		Ok(header) => header,
 		Err(_) => {
+			// While subscribing should succeed the first time around, we ran into some cases where
+			// it didn't. Since we can't proceed without subscribing, we try again after a delay
+			// and panic if it still fails.
 			std::thread::sleep(Duration::from_secs(3));
 			get_electrsd().client.block_headers_subscribe().expect("failed to subscribe to block headers")
 		}