InvocationError: could not find executable None

[Stéphane Caron]

Thanks to the community behind tox-conda for developing this tool! I'm trying it in a project where it could ease a lot of things if conda worked, using micromamba as the local conda exe. Package installation seems to go fine, but after that tox fails with this error:

ERROR: FAIL could not package project - v = InvocationError('could not find executable None', None)

Details:

CONDA_EXE=${HOME}/.local/bin/micromamba tox -v run -e py
using tox.ini: /home/user/src/pink/tox.ini (pid 57426)
using tox-3.28.0 from /home/user/.local/lib/python3.10/site-packages/tox/__init__.py (pid 57426)
.package cannot reuse: no previous config /home/user/src/pink/.tox/.package/.tox-config1
.package create: /home/user/src/pink/.tox/.package
[57435] /home/user/src/pink/.tox$ /home/user/.local/bin/micromamba create --yes -p .package --channel conda-forge python=3.10 >.package/log/.package-0.log
.package installcondadeps: numpy >=1.26.2, pinocchio >=2.6.4, qpsolvers >=2.7.2, quadprog >=0.1.11, robot_descriptions >=1.9.0
[57478] /home/user/src/pink/.tox$ /home/user/.local/bin/micromamba install --quiet --yes -p .package --channel conda-forge --override-channels python=3.10 'numpy >=1.26.2' 'pinocchio >=2.6.4' 'qpsolvers >=2.7.2' 'quadprog >=0.1.11' 'robot_descriptions >=1.9.0' >.package/log/.package-1.log
.package installdeps: flit_core >=2,<4
[57515] /home/user/src/pink$ /usr/bin/python -m pip install 'flit_core >=2,<4' >.tox/.package/log/.package-2.log
write config to /home/user/src/pink/.tox/.package/.tox-config1 as '45692c3da2492563eabf0a8f5dc18d20dc9c34ffe3a18202563e00bae684be91 /usr/bin/python3\n3.28.0 0 0 0\n00000000000000000000000000000000 flit_core >=2,<4\n00000000000000000000000000000000 numpy >=1.26.2\n00000000000000000000000000000000 pinocchio >=2.6.4\n00000000000000000000000000000000 qpsolvers >=2.7.2\n00000000000000000000000000000000 quadprog >=0.1.11\n00000000000000000000000000000000 robot_descriptions >=1.9.0'
ERROR: FAIL could not package project - v = InvocationError('could not find executable None', None)

And here is the tox.ini and the .tox directory.

As far as I can tell there is no error message in .tox logs. What could be the None executable mentioned in the error?