Update README file

[andreufont]

I tried to install Picca at NERSC and failed.

First, it wasn't clear which version of python I should use (the README does not specify it).

I tried python==3.8 and followed the instructions, but the code crashed when pip installing Picca:

      /global/homes/f/font/.conda/envs/my_picca_env/compiler_compat/ld: /usr/lib/../lib64/crti.o: unable to initialize decompress status for section .debug_aranges
      /usr/lib/../lib64/crti.o: file not recognized: file format not recognized
      collect2: error: ld returned 1 exit status
      error: command '/opt/cray/pe/gcc/11.2.0/bin/gcc' failed with exit code 1
      [end of output]

  note: This error originates from a subprocess, and is likely not a problem with pip.
  ERROR: Failed building wheel for fitsio
  Running setup.py clean for fitsio
  Building wheel for future (setup.py) ... done
  Created wheel for future: filename=future-0.18.3-py3-none-any.whl size=492024 sha256=97610f38c6f91a65b3bb1ca68ad9da699393a2cffeb0f43187f05854f419f04b
  Stored in directory: /global/u2/f/font/.cache/pip/wheels/a0/0b/ee/e6994fadb42c1354dcccb139b0bf2795271bddfe6253ccdf11
Successfully built future
Failed to build fitsio
ERROR: Could not build wheels for fitsio, which is required to install pyproject.toml-based projects

[Waelthus]

Indeed, python 3.8 might be to old by now, the testing suite currently runs 3.9, 3.10 and 3.11 and works fine on all. Not sure anymore why exactly 3.8 should fail, but note that perlmutter does not ship a 3.8 module anymore (see module avail python), so it might well be that library versions required for compiling older code are missing as well...

I just tried the following which on first glance seems to have worked:

module load python/3.11
mamba create -n test python==3.11
mamba activate test
pip install picca

can you confirm this is fine for you as well?

[Waelthus]

I added the version requirement to the README text

[andreufont]

I confirm that it works with 3.10. Thanks!