MacOS 15.5

Log:

./mach bootstrap --no-system-changes

Note on Artifact Mode:

Artifact builds download prebuilt C++ components rather than building
them locally. Artifact builds are faster!

Artifact builds are recommended for people working on Firefox or
Firefox for Android frontends, or the GeckoView Java API. They are unsuitable
for those working on C++ code. For more information see:
https://developer.mozilla.org/en-US/docs/Artifact_builds.

Please choose the version of Firefox you want to build:
  1. Firefox for Desktop Artifact Mode
  2. Firefox for Desktop
  3. GeckoView/Firefox for Android Artifact Mode
  4. GeckoView/Firefox for Android
Your choice: 4
Your version of Python 3 (3.7.3) is new enough.
Your version of Python 2 (2.7.17) is new enough.
virtualenv at /Users/asferro/.mozbuild/_virtualenvs/mach is already up to date.
Traceback (most recent call last):
  File "/Users/asferro/.mozbuild/_virtualenvs/mach/bin/pip", line 5, in <module>
    from pip._internal.cli.main import main
ModuleNotFoundError: No module named 'pip._internal.cli.main'
Error running mach:

    ['create-mach-environment']

The error occurred in code that was called by the mach command. This is either
a bug in the called code itself or in the way that mach is calling it.
You can invoke |./mach busted| to check if this issue is already on file. If it
isn't, please use |./mach busted file create-mach-environment| to report it. If |./mach busted| is
misbehaving, you can also inspect the dependencies of bug 1543241.

If filing a bug, please include the full output of mach, including this error
message.

The details of the failure are as follows:

subprocess.CalledProcessError: Command '['/Users/asferro/.mozbuild/_virtualenvs/mach/bin/pip', 'install', 'zstandard>=0.9.0,<=0.13.0']' returned non-zero exit status 1.

  File "/Users/asferro/workspace/mozilla-central/python/mozbuild/mozbuild/mach_commands.py", line 1549, in create_mach_environment
    manager.install_pip_package('zstandard>=0.9.0,<=0.13.0')
  File "/Users/asferro/workspace/mozilla-central/python/mozbuild/mozbuild/virtualenv.py", line 578, in install_pip_package
    return self._run_pip(args)
  File "/Users/asferro/workspace/mozilla-central/python/mozbuild/mozbuild/virtualenv.py", line 624, in _run_pip
    universal_newlines=PY3)
  File "/Applications/Xcode.app/Contents/Developer/Library/Frameworks/Python3.framework/Versions/3.7/lib/python3.7/subprocess.py", line 347, in check_call
    raise CalledProcessError(retcode, cmd)
Error running mach:

    ['bootstrap', '--no-system-changes']

The error occurred in code that was called by the mach command. This is either
a bug in the called code itself or in the way that mach is calling it.
You can invoke |./mach busted| to check if this issue is already on file. If it
isn't, please use |./mach busted file bootstrap| to report it. If |./mach busted| is
misbehaving, you can also inspect the dependencies of bug 1543241.

If filing a bug, please include the full output of mach, including this error
message.

The details of the failure are as follows:

subprocess.CalledProcessError: Command '['/Applications/Xcode.app/Contents/Developer/usr/bin/python3', '/Users/asferro/workspace/mozilla-central/mach', 'create-mach-environment']' returned non-zero exit status 1.

  File "/Users/asferro/workspace/mozilla-central/python/mozboot/mozboot/mach_commands.py", line 45, in bootstrap
    bootstrapper.bootstrap()
  File "/Users/asferro/workspace/mozilla-central/python/mozboot/mozboot/bootstrap.py", line 368, in bootstrap
    self.instance.ensure_mach_environment(checkout_root)
  File "/Users/asferro/workspace/mozilla-central/python/mozboot/mozboot/base.py", line 277, in ensure_mach_environment
    subprocess.check_call(cmd, cwd=checkout_root)
  File "/Applications/Xcode.app/Contents/Developer/Library/Frameworks/Python3.framework/Versions/3.7/lib/python3.7/subprocess.py", line 347, in check_call
    raise CalledProcessError(retcode, cmd)

Note: if I rm -rf ~/.mozbuild/_virtualenvs it works the first time, then fails again with the above error.

Hey Agi! I'm currently digging into a related issue over here.
The active workaround is to use brew python instead of Xcode python.