Prior to wait_test branch.

Author: peterhinch

README.md

@@ -462,7 +462,7 @@ Methods (asynchronous):
  1. `readline` No args. Pauses until data received. Returns a line.
  2. `write` Args: `buf`, `qos=True`, `wait=True`. `buf` holds a line of text.  
  If `qos` is set, the system guarantees delivery. If it is clear messages may
- (rarely) be lost in the event of an outage.__
+ (rarely) be lost in the event of an outage.  
  The `wait` arg determines the behaviour when multiple concurrent writes are
  launched with `qos` set. See [Quality of service](./README.md#7-quality-of-service).
 

iot/client.mpy

@@ -220,7 +220,6 @@ async def _write(self, line):
 
             # send fail. _send has triggered _evfail. .run clears _evok.
             await asyncio.sleep_ms(0)  # Ensure .run is scheduled
-            assert not self._evok.is_set()  # TEST
 
     # Handle qos. Retransmit until matching ACK received.
     # ACKs typically take 200-400ms to arrive.