BUG: On Py3.10 importing `scipy.x` fails

Describe your issue.

Importing scipy.signal under Py3.10 (in a venv) fails with this message (on Py3.9.4 and older it works):

$ python3
Python 3.10.0a6 (default, Mar  2 2021, 02:01:08) [GCC 5.4.0 20160609] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import scipy.signal
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "~/vgl310/lib/python3.10/site-packages/scipy/signal/__init__.py", line 302, in <module>
    from .filter_design import *
  File "~/vgl310/lib/python3.10/site-packages/scipy/signal/filter_design.py", line 16, in <module>
    from scipy import special, optimize, fft as sp_fft
  File "~/vgl310/lib/python3.10/site-packages/scipy/optimize/__init__.py", line 421, in <module>
    from ._shgo import shgo
  File "~/vgl310/lib/python3.10/site-packages/scipy/optimize/_shgo.py", line 9, in <module>
    from scipy import spatial
  File "~/vgl310/lib/python3.10/site-packages/scipy/spatial/__init__.py", line 107, in <module>
    from . import distance, transform
  File "/home/ullix/geigerlog/vgl310/lib/python3.10/site-packages/scipy/spatial/transform/__init__.py", line 19, in <module>
    from .rotation import Rotation, Slerp
ImportError: /home/ullix/geigerlog/vgl310/lib/python3.10/site-packages/scipy/spatial/transform/rotation.cpython-310-x86_64-linux-gnu.so: undefined symbol: _PyGen_Send

The latest version of scipy is installed:

$ python3 -m pip install -U scipy
Requirement already satisfied: scipy in ~/vgl310/lib/python3.10/site-packages (1.6.1)
Requirement already satisfied: numpy>=1.16.5 in ~/vgl310/lib/python3.10/site-packages (from scipy) (1.21.2)

Reproducing Code Example

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Error message

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SciPy/NumPy/Python version information

import sys, scipy, numpy; print(scipy.__version__, numpy.__version__, sys.version_info) 1.6.1 1.21.2 sys.version_info(major=3, minor=10, micro=0, releaselevel='alpha', serial=6)

[tupui]

pip install git+https://github.com/scipy/scipy solves the issue for me. A new release would be great 👍

Note that not having a release of scipy on pypi makes it hard for downstream projects to test with 3.10 …

A release is in the making (cf the branch 1.7.2 and #14567). It just takes time out of our limited resources.

[rgommers]

1.7.2 is released, closing.