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Port, board and/or hardware

RP2, Pyboard 1.1

MicroPython version

MicroPython v1.22.0 on 2023-12-27; Raspberry Pi Pico with RP2040

Reproduction

Create a file rats15.py on the PC:

import os
fn = "delete_me"
with open(fn, "wb") as f:
    f.write(b"hello\n\xde\xad\xbe\xef")
with open(fn, "rb") as f:
    print(f.readline())
    print(f.read(4))
os.unlink(fn)

Run mpremote

$ mpremote mount .

At the REPL issue

import rats15

Expected behaviour

>>> import rats15
b'hello\n'
b'\xde\xad\xbe\xef'
>>> 

This occurs if the script is run under CPython, under the Unix build, or if run locally on a MP target.

Observed behaviour

When run as described above via mpremote mount .:

MicroPython v1.22.2 on 2024-02-22; Raspberry Pi Pico with RP2040
Type "help()" for more information.
>>> import rats15
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "rats15.py", line 7, in <module>
  File "<stdin>", line 147, in readline
TypeError: unsupported types for __add__: 'str', 'bytes'
>>> 

Additional Information

mpremote is V1.22.0. The fault occurs on readline(). It originally became evident accessing a pgm graphics file which contains four lines of \n terminated ASCII text followed by binary data