Setuptools issue building numpy

Reproduce with buildozer android debug using the shown requirements and Android settings, then focus on the numpy build step and its isolated environment where setuptools.build_meta cannot be imported. Compare the installed build dependencies and the hostpython3 invocation; done means the same configuration completes the numpy wheel build.

Ubuntu 24.04
Python 3.12.3

requirements = python3,kivy,numpy
android.minapi = 24
android.ndk_api = 24
android.archs = arm64-v8a
p4a.branch = develop

(venv3) ~/ex/hello>pip list
Package      Version
------------ -------
buildozer    1.5.0
Cython       3.0.12
distlib      0.3.9
filelock     3.17.0
pexpect      4.9.0
pip          25.0.1
platformdirs 4.3.6
ptyprocess   0.7.0
setuptools   75.8.2
sh           2.2.2
virtualenv   20.29.3

buildozer android debug

Starts well....

[INFO]:    Building numpy for arm64-v8a
[INFO]:    numpy apparently isn't already in site-packages
[INFO]:    Writing cross file at: /tmp/android.meson.cross
[DEBUG]:   -> running pip install build[virtualenv] pip Cython>=3.0.6 ninja==1.11.1.1 meson==1.4.0 --target /home/bobf/ex/hello/.buildozer/android/platform/build-arm64-v8a/build/other_builds/hostpython3/desktop/hostpython3/native-build/Lib/site-packages --python-version 3.11.5 --only-binary=:all: --upgrade
[DEBUG]:        Collecting pip
[DEBUG]:          Using cached pip-25.0.1-py3-none-any.whl.metadata (3.7 kB)
[DEBUG]:        Collecting Cython>=3.0.6
[DEBUG]:          Using cached Cython-3.0.12-cp311-cp311-manylinux_2_17_x86_64.manylinux2014_x86_64.whl.metadata (3.3 kB)
[DEBUG]:        Collecting ninja==1.11.1.1
[DEBUG]:          Using cached ninja-1.11.1.1-py2.py3-none-manylinux1_x86_64.manylinux_2_5_x86_64.whl.metadata (5.3 kB)
[DEBUG]:        Collecting meson==1.4.0
[DEBUG]:          Using cached meson-1.4.0-py3-none-any.whl.metadata (1.8 kB)
[DEBUG]:        Collecting build[virtualenv]
[DEBUG]:          Using cached build-1.2.2.post1-py3-none-any.whl.metadata (6.5 kB)
[DEBUG]:        Collecting packaging>=19.1 (from build[virtualenv])
[DEBUG]:          Using cached packaging-24.2-py3-none-any.whl.metadata (3.2 kB)
[DEBUG]:        Collecting pyproject_hooks (from build[virtualenv])
[DEBUG]:          Using cached pyproject_hooks-1.2.0-py3-none-any.whl.metadata (1.3 kB)
[DEBUG]:        Collecting virtualenv>=20.0.35 (from build[virtualenv])
[DEBUG]:          Using cached virtualenv-20.29.3-py3-none-any.whl.metadata (4.5 kB)
[DEBUG]:        Collecting distlib<1,>=0.3.7 (from virtualenv>=20.0.35->build[virtualenv])
[DEBUG]:          Using cached distlib-0.3.9-py2.py3-none-any.whl.metadata (5.2 kB)
[DEBUG]:        Collecting filelock<4,>=3.12.2 (from virtualenv>=20.0.35->build[virtualenv])
[DEBUG]:          Using cached filelock-3.17.0-py3-none-any.whl.metadata (2.9 kB)
[DEBUG]:        Collecting platformdirs<5,>=3.9.1 (from virtualenv>=20.0.35->build[virtualenv])
[DEBUG]:          Using cached platformdirs-4.3.6-py3-none-any.whl.metadata (11 kB)
[DEBUG]:        Using cached ninja-1.11.1.1-py2.py3-none-manylinux1_x86_64.manylinux_2_5_x86_64.whl (307 kB)
[DEBUG]:        Using cached meson-1.4.0-py3-none-any.whl (935 kB)
[DEBUG]:        Using cached pip-25.0.1-py3-none-any.whl (1.8 MB)
[DEBUG]:        Using cached Cython-3.0.12-cp311-cp311-manylinux_2_17_x86_64.manylinux2014_x86_64.whl (3.6 MB)
[DEBUG]:        Using cached packaging-24.2-py3-none-any.whl (65 kB)
[DEBUG]:        Using cached virtualenv-20.29.3-py3-none-any.whl (4.3 MB)
[DEBUG]:        Using cached build-1.2.2.post1-py3-none-any.whl (22 kB)
[DEBUG]:        Using cached pyproject_hooks-1.2.0-py3-none-any.whl (10 kB)
[DEBUG]:        Using cached distlib-0.3.9-py2.py3-none-any.whl (468 kB)
[DEBUG]:        Using cached filelock-3.17.0-py3-none-any.whl (16 kB)
[DEBUG]:        Using cached platformdirs-4.3.6-py3-none-any.whl (18 kB)
[DEBUG]:        Installing collected packages: ninja, distlib, pyproject_hooks, platformdirs, pip, packaging, meson, filelock, Cython, virtualenv, build
[DEBUG]:        Successfully installed Cython-3.0.12 build-1.2.2.post1 distlib-0.3.9 filelock-3.17.0 meson-1.4.0 ninja-1.11.1.1 packaging-24.2 pip-25.0.1 platformdirs-4.3.6 pyproject_hooks-1.2.0 virtualenv-20.29.3

But fails with:

[INFO]:    -> directory context /home/bobf/ex/hello/.buildozer/android/platform/build-arm64-v8a/build/other_builds/numpy/arm64-v8a__ndk_target_24/numpy
[DEBUG]:   -> running python3 -m build --wheel --config-setting builddir=/home/bobf/ex/hello/.buildozer/android/platform/build-arm64-v8a/build/other_builds/numpy/arm64-v8a__ndk_target_24/numpy/p4a_android_build -Csetup-args=-Dblas=none -Csetup-args=-Dlapack=none -Csetup-args=--cross-file -Csetup-args=/tmp/android.meson.cross
[DEBUG]:        * Creating isolated environment: venv+pip...
[DEBUG]:        * Installing packages in isolated environment:
[DEBUG]:          - Cython>=0.29.34,<3.1
[DEBUG]:          - meson-python>=0.15.0,<0.16.0
[DEBUG]:        * Getting build dependencies for wheel...
[DEBUG]:        Ignoring "sys._home = value" override
[DEBUG]:        * Installing packages in isolated environment:
[DEBUG]:          - patchelf >= 0.11.0
[DEBUG]:        > /home/bobf/ex/hello/.buildozer/android/platform/build-arm64-
[DEBUG]:          v8a/build/other_builds/python3/arm64-v8a__ndk_target_24/python3/android-
[DEBUG]:          build/python3 -m pip --python /tmp/build-env-cuoq9kcw/bin/python install
[DEBUG]:          --use-pep517 --no-warn-script-location --no-compile -r /tmp/build-
[DEBUG]:          reqs-f105xuxq.txt
[DEBUG]:        < Collecting patchelf>=0.11.0 (from -r /tmp/build-reqs-f105xuxq.txt (line 1))
[DEBUG]:        <   Using cached patchelf-0.17.2.1.tar.gz (167 kB)
[DEBUG]:        <   Installing build dependencies: started
[DEBUG]:        <   Installing build dependencies: finished with status 'done'
[DEBUG]:        <   Getting requirements to build wheel: started
[DEBUG]:        <   Getting requirements to build wheel: finished with status 'done'
[DEBUG]:        < Ignoring "sys._home = value" override
[DEBUG]:        < ERROR: Exception:
[DEBUG]:        < Traceback (most recent call last):
[DEBUG]:        <   File "/home/bobf/ex/hello/.buildozer/android/platform/build-
[DEBUG]:          arm64-v8a/build/other_builds/hostpython3/desktop/hostpython3/native-
[DEBUG]:          build/Lib/site-packages/pip/_internal/cli/base_command.py", line 106, in
[DEBUG]:          _run_wrapper

(many lines deleted for brevity)

[DEBUG]:        <   File "/home/bobf/ex/hello/.buildozer/android/platform/build-
[DEBUG]:          arm64-v8a/build/other_builds/hostpython3/desktop/hostpython3/native-
[DEBUG]:          build/Lib/site-packages/pip/_vendor/pyproject_hooks/_impl.py", line 402, in
[DEBUG]:          _call_hook
[DEBUG]:        <     raise BackendUnavailable(
[DEBUG]:        < pip._vendor.pyproject_hooks._impl.BackendUnavailable: Cannot import
[DEBUG]:          'setuptools.build_meta'
[DEBUG]:

In addition to the user installed setuptools==75.8.2, the build did download setuptools==69.2.0. But I don't see any evidence of it in the "isolated environment", which of course doesn't mean it isn't there!

Google shows me this message occurs occasionally and in many contexts. Generally attributed to some unknown pip issue. I wondered if something was corrupted, so I created a new Ubuntu 22.04 instance, but this did not change the behavior.