configure script breaks with Python 3.10

[leahneukirchen]

Describe the bug

The configure script doesn't detect Python 3.10 properly.

To Reproduce
Steps to reproduce the behavior:

• install python3.10
• ./configure --with-python

checking for a Python interpreter with version >= 2.3... python                 
checking for python... /usr/bin/python                                          
checking for python version... 3.1                                              
checking for python platform... linux                                           
checking for python script directory... ${prefix}/lib/python3.10/site-packages  
checking for python extension module directory... ${exec_prefix}/lib/python3.10/
site-packages                                                                   
checking for headers required to compile python extensions... not found         
configure: WARNING: could not find Python headers                               

Expected behavior

checking for python version... 3.10
...
checking for headers required to compile python extensions... found

Desktop (please complete the following information):

• OS: Void Linux x86_64/glibc

Additional context

The test hardcodes three characters for the python version:

  am_cv_python_version=`$PYTHON -c "import sys; sys.stdout.write(sys.version[:3])"`

As a workaround, one can pass am_cv_python_version=3.10 to ./configure, then it works fine.

You should update the AM_PATH_PYTHON in aclocal.m4.

[c72578]

@leahneukirchen this does not look like an issue caused by RRDtool.
See a current Fedora build log [1]:

checking for a Python interpreter with version >= 2.3... python3
checking for python3... /usr/bin/python3
checking for python3 version... 3.10
checking for python3 platform... linux
checking for python3 script directory... ${prefix}/lib/python3.10/site-packages
checking for python3 extension module directory... ${exec_prefix}/lib64/python3.10/site-packages
checking for headers required to compile python extensions... found

Involved package versions, e.g. automake 1.16.2 [2]

[1] https://kojipkgs.fedoraproject.org//packages/rrdtool/1.7.2/21.fc35/data/logs/x86_64/build.log
[2] https://kojipkgs.fedoraproject.org//packages/rrdtool/1.7.2/21.fc35/data/logs/x86_64/root.log

[c72578]

This is how it has been fixed in Fedora for automake-1.16.2:
https://src.fedoraproject.org/rpms/automake/c/3327906e94b767330433fda3da2d0997292c55ad?branch=rawhide

Upstream fix:
python: determine Python (3.10) version number correctly.
https://git.savannah.gnu.org/cgit/automake.git/commit/?id=e21d46fddd0753e66a4acda88317670fee07f3e6
This fix is included in automake 1.16.3 and 1.16.4

[leahneukirchen]

Yes, reconfiguring with a new automake fixes it.

Still, the configure script in the latest release tarball is broken.

[c72578]

In order to avoid this, ./bootstrap should be run first.