# Buggy code
def minimum_sys_modules(cls, site_libs, modules=None):
    """Given a set of site-packages paths, return a "clean" sys.modules.

    When importing site, modules within sys.modules have their __path__'s populated with
    additional paths as defined by *-nspkg.pth in site-packages, or alternately by distribution
    metadata such as *.dist-info/namespace_packages.txt.  This can possibly cause namespace
    packages to leak into imports despite being scrubbed from sys.path.

    NOTE: This method mutates modules' __path__ attributes in sys.module, so this is currently an
    irreversible operation.
    """

    modules = modules or sys.modules
    new_modules = {}

    for module_name, module in modules.items():
        # builtins can stay
        if not hasattr(module, "__path__"):
            new_modules[module_name] = module
            continue

        # Unexpected objects, e.g. namespace packages, should just be dropped:
        if not isinstance(module.__path__, list):
            TRACER.log("Dropping %s" % (module_name,), V=3)
            continue

        # Pop off site-impacting __path__ elements in-place.
        for k in reversed(range(len(module.__path__))):
            if cls._tainted_path(module.__path__[k], site_libs):
                TRACER.log(
                    "Scrubbing %s.__path__: %s" % (module_name, module.__path__[k]), V=3
                )
                module.__path__.pop(k)

        # It still contains path elements not in site packages, so it can stay in sys.modules
        if module.__path__:
            new_modules[module_name] = module

    return new_modules


# Traceback (AttributeError)
Traceback (most recent call last):
File ".bootstrap/_pex/pex.py", line 364, in execute
File ".bootstrap/_pex/pex.py", line 90, in _activate
File ".bootstrap/_pex/environment.py", line 147, in activate
File ".bootstrap/_pex/environment.py", line 198, in _activate
File ".bootstrap/_pex/environment.py", line 64, in update_module_paths
AttributeError: '_NamespacePath' object has no attribute 'insert'

# Fixed code
def minimum_sys_modules(cls, site_libs, modules=None):
    """Given a set of site-packages paths, return a "clean" sys.modules.

    When importing site, modules within sys.modules have their __path__'s populated with
    additional paths as defined by *-nspkg.pth in site-packages, or alternately by distribution
    metadata such as *.dist-info/namespace_packages.txt.  This can possibly cause namespace
    packages to leak into imports despite being scrubbed from sys.path.

    NOTE: This method mutates modules' __path__ attributes in sys.modules, so this is currently an
    irreversible operation.
    """

    modules = modules or sys.modules
    new_modules = {}

    for module_name, module in modules.items():
        # builtins can stay
        if not hasattr(module, "__path__"):
            new_modules[module_name] = module
            continue

        # Unexpected objects, e.g. PEP 420 namespace packages, should just be dropped.
        if not isinstance(module.__path__, list):
            TRACER.log("Dropping %s" % (module_name,), V=3)
            continue

        # Pop off site-impacting __path__ elements in-place.
        for k in reversed(range(len(module.__path__))):
            if cls._tainted_path(module.__path__[k], site_libs):
                TRACER.log(
                    "Scrubbing %s.__path__: %s" % (module_name, module.__path__[k]), V=3
                )
                module.__path__.pop(k)

        # It still contains path elements not in site packages, so it can stay in sys.modules
        if module.__path__:
            new_modules[module_name] = module

    return new_modules