circuitpython: DHT22 driver not working under CP3.0-alpha

dht_simpletest yields:

Adafruit CircuitPython 3.0.0-alpha.3-31-g8b6aeb9-dirty on 2018-03-26; Adafruit Feather M0 Express with samd21g18
>>> 
>>> 
>>> import dht_simpletest
('A full buffer was not returned.  Try again.',)
('A full buffer was not returned.  Try again.',)
('A full buffer was not returned.  Try again.',)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "dht_simpletest.py", line 18, in <module>
KeyboardInterrupt: 
>>> 

under CP3.0 alpha
It works ok on 2.2.4.