This applies the mpremote commit 0d46e45a1f
to pyboard.py.
If the target does not return any data then `read_until()` will block
indefinitely. Fix this by making the initial read part of the general read
look, which always checks `inWaiting() > 0` before reading from the serial
device.
Also added the UART timeout to the constructor. This is not currently used
but may be used as an additional safeguard.
Signed-off-by: Damien George <damien@micropython.org>
aaedd59b7c