gh-151253: Dump the Python path configuration on _PyCodec_InitRegistry() failure

[vstinner]

If "import encodings" fails, dump the Python path configuration to help users debugging their configuration. The encodings module (package) is the first module imported during Python startup.

• Issue: Dump the path configuration at Python startup if import encodings fails #151253

[vstinner]

Example before the change:

$ PYTHONHOME=/xyz ./python 
WARN: Could not find the standard library directory! The Python 'home' directory was set to '/xyz', is this correct?
Fatal Python error: Failed to import encodings module
Python runtime state: core initialized
Exception ignored in the internal traceback machinery:
ModuleNotFoundError: No module named 'traceback'
ModuleNotFoundError: No module named 'encodings'

Current thread 0x00007f58ef90c780 [python] (most recent call first):

Example with the change:

$ PYTHONHOME=/xyz ./python 
WARN: Could not find the standard library directory! The Python 'home' directory was set to '/xyz', is this correct?
Python path configuration:
  PYTHONHOME = '/xyz'
  PYTHONPATH = (not set)
  program name = './python'
  isolated = 0
  environment = 1
  user site = 1
  safe_path = 0
  import site = 1
  is in build tree = 1
  stdlib dir = '/xyz/lib/python3.16'
  sys.path[0] = (not set)
  sys._base_executable = '/home/vstinner/python/main/python'
  sys.base_prefix = '/usr/local'
  sys.base_exec_prefix = '/usr/local'
  sys.platlibdir = 'lib'
  sys.executable = '/home/vstinner/python/main/python'
  sys.prefix = '/usr/local'
  sys.exec_prefix = '/usr/local'
  sys.path = [
    '/usr/local/lib/python316.zip',
    '/xyz/lib/python3.16',
    '/home/vstinner/python/main/build/lib.linux-x86_64-3.16',
  ]
Fatal Python error: Failed to import encodings module
Python runtime state: core initialized
Exception ignored in the internal traceback machinery:
ModuleNotFoundError: No module named 'traceback'
ModuleNotFoundError: No module named 'encodings'

Current thread 0x00007f798489e780 [python] (most recent call first):

[vstinner]

Before, init_fs_encoding() was the first function importing a module: if config_get_codec_name() fails, call _Py_DumpPathConfig(). commit f8290df changed Python startup to call _PyCodecRegistry_Init() at startup, before config_get_codec_name().

[vstinner]

test_cmd_line.test_dump_path_config() failed on:

• Windows / Build and test (x64, tail-call)
• Windows (free-threading) / Build and test (x64, tail-call)
• Address sanitizer (ubuntu-24.04)

[miss-islington-app]

Thanks @vstinner for the PR 🌮🎉.. I'm working now to backport this PR to: 3.13, 3.14, 3.15.
🐍🍒⛏🤖

[miss-islington-app]

Sorry, @vstinner, I could not cleanly backport this to 3.15 due to a conflict.
Please backport using cherry_picker on command line.

cherry_picker 7b6e98911e1485be13817f2aedbbfadb1c4ea876 3.15

[miss-islington-app]

Sorry, @vstinner, I could not cleanly backport this to 3.14 due to a conflict.
Please backport using cherry_picker on command line.

cherry_picker 7b6e98911e1485be13817f2aedbbfadb1c4ea876 3.14

[miss-islington-app]

Sorry, @vstinner, I could not cleanly backport this to 3.13 due to a conflict.
Please backport using cherry_picker on command line.

cherry_picker 7b6e98911e1485be13817f2aedbbfadb1c4ea876 3.13

[bedevere-app]

GH-151269 is a backport of this pull request to the 3.15 branch.