tools/mpremote: Fix mpremote mip install with multiple lib folders in sys.path.

[Josverl]

This is a fix for an algorithmic error in mpremote mip,
that throws an error due to a \n used in the concatenation and split.

The issue is is discussed in https://github.com/orgs/micropython/discussions/14078

Repro & manual test:

• connect a pybv11 with an SD card
  on start the pybv11 will mount the SD card and add a 2nd ../lib-path to sys.path, which will trigger the error.
  sys.path : ['', '.frozen', '/sd', '/sd/lib', '/flash', '/flash/lib']

• mpremote mip install requests

  • Expected result:

    Install requests
    Installing requests (latest) from https://micropython.org/pi/v2 to /sd/lib
    Installing: /sd/lib/requests/__init__.mpy
    Done
    

Sample error without this fix

Install requests
Installing requests (latest) from https://micropython.org/pi/v2 to /sd/lib
/requests/init.mpy
Traceback (most recent call last):
File "", line 198, in _run_module_as_main
File "", line 88, in run_code
File "C:\Users\josverl\pipx.cache\493badebc2c62e8\Scripts\mpremote.exe_main.py", line 7, in
File "C:\Users\josverl\pipx.cache\493badebc2c62e8\Lib\site-packages\mpremote\main.py", line 528, in main
handler_func(state, args)
File "C:\Users\josverl\pipx.cache\493badebc2c62e8\Lib\site-packages\mpremote\mip.py", line 197, in do_mip
_install_package(
File "C:\Users\josverl\pipx.cache\493badebc2c62e8\Lib\site-packages\mpremote\mip.py", line 160, in _install_package
_install_json(transport, package, index, target, version, mpy)
File "C:\Users\josverl\pipx.cache\493badebc2c62e8\Lib\site-packages\mpremote\mip.py", line 118, in _install_json
_download_file(transport, file_url, fs_target_path)
File "C:\Users\josverl\pipx.cache\493badebc2c62e8\Lib\site-packages\mpremote\mip.py", line 91, in _download_file
_ensure_path_exists(transport, dest)
File "C:\Users\josverl\pipx.cache\493badebc2c62e8\Lib\site-packages\mpremote\mip.py", line 33, in _ensure_path_exists
transport.fs_mkdir(prefix)
File "C:\Users\josverl\pipx.cache\493badebc2c62e8\Lib\site-packages\mpremote\transport_serial.py", line 427, in fs_mkdir
self.exec("import os\nos.mkdir('%s')" % dir)
File "C:\Users\josverl\pipx.cache\493badebc2c62e8\Lib\site-packages\mpremote\transport_serial.py", line 287, in exec
raise TransportError("exception", ret, ret_err)
mpremote.transport.TransportError: ('exception', b'', b'Traceback (most recent call last):\r\n File "", line 2\r\nSyntaxError: invalid syntax\r\n')

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 98.42%. Comparing base (b4213c9) to head (85f29ab).

❗ Current head 85f29ab differs from pull request most recent head 3af1425

Please upload reports for the commit 3af1425 to get more accurate results.

Additional details and impacted files

@@            Coverage Diff             @@
##           master   #15332      +/-   ##
==========================================
- Coverage   98.42%   98.42%   -0.01%     
==========================================
  Files         161      161              
  Lines       21249    21234      -15     
==========================================
- Hits        20915    20900      -15     
  Misses        334      334              

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[github-actions]

Code size report:

   bare-arm:    +0 +0.000% 
minimal x86:    +0 +0.000% 
   unix x64:    +0 +0.000% standard
      stm32:    +0 +0.000% PYBV10
     mimxrt:    +0 +0.000% TEENSY40
        rp2:    +0 +0.000% RPI_PICO_W
       samd:    +0 +0.000% ADAFRUIT_ITSYBITSY_M4_EXPRESS

[dpgeorge]

Thanks for the fix. This looks reasonable to me, using | as the separator. That character is unlikely to be in the name of any path.