Error upgrading from 2.2.8. to 2.3

I got an error executing the “pip install -U indico” comand in our Debian 9 test environment.

Collecting alembic==1.4.2
  Using cached alembic-1.4.2.tar.gz (1.1 MB)
  Installing build dependencies ... done
  Getting requirements to build wheel ... error
  ERROR: Command errored out with exit status 1:
   command: /opt/indico/.venv/bin/python2 /opt/indico/.venv/local/lib/python2.7/site-packages/pip/_vendor/pep517/ get_requires_for_build_wheel /tmp/tmp7swB0y
       cwd: /tmp/pip-install-b40tjn/alembic
  Complete output (10 lines):
  Traceback (most recent call last):
    File "/opt/indico/.venv/local/lib/python2.7/site-packages/pip/_vendor/pep517/", line 280, in <module>
    File "/opt/indico/.venv/local/lib/python2.7/site-packages/pip/_vendor/pep517/", line 263, in main
      json_out['return_val'] = hook(**hook_input['kwargs'])
    File "/opt/indico/.venv/local/lib/python2.7/site-packages/pip/_vendor/pep517/", line 108, in get_requires_for_build_wheel
      backend = _build_backend()
    File "/opt/indico/.venv/local/lib/python2.7/site-packages/pip/_vendor/pep517/", line 99, in _build_backend
      obj = getattr(obj, path_part)
  AttributeError: 'module' object has no attribute '__legacy__'
ERROR: Command errored out with exit status 1: /opt/indico/.venv/bin/python2 /opt/indico/.venv/local/lib/python2.7/site-packages/pip/_vendor/pep517/ get_requires_for_build_wheel /tmp/tmp7swB0y Check the logs for full command output.

Indico 2.2.8
Debian 9
pip 20.2.3
Python 2.7.13

Can you help me please?
Alberto Nardella

I’ve never seen this error before. Try upgrading pip and setuptools first, even though your versions aren’t that old… pip install -U pip setuptools

It worked. Thank you