Complications with pyshtools dependency

[jluethi]

The pyshtools dependency needed for spatial harmonics calculations can lead to tricky installation issues due to Fortran compiler requirements. It's fine locally for me so far and on the FMI cluster.

On the Pelkmans lab cluster, I run into the following issue:

> conda create -n scmultiplex-test python=3.10 -y
> conda activate scmultiplex-test
> pip install pyshtools
Collecting pyshtools
  Downloading pyshtools-4.13.1.tar.gz (41.6 MB)
     ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ 41.6/41.6 MB 26.8 MB/s eta 0:00:00
  Installing build dependencies ... done
  Getting requirements to build wheel ... done
  Installing backend dependencies ... done
  Preparing metadata (pyproject.toml) ... error
  error: subprocess-exited-with-error
  
  × Preparing metadata (pyproject.toml) did not run successfully.
  │ exit code: 1
  ╰─> [30 lines of output]
      + meson setup /tmp/pip-install-_qx6zrjm/pyshtools_a29c52ebf9ee40809aa559b8f9a4386d /tmp/pip-install-_qx6zrjm/pyshtools_a29c52ebf9ee40809aa559b8f9a4386d/.mesonpy-szpr5sls -Dbuildtype=release -Db_ndebug=if-release -Db_vscrt=md --default-library=static --native-file=/tmp/pip-install-_qx6zrjm/pyshtools_a29c52ebf9ee40809aa559b8f9a4386d/.mesonpy-szpr5sls/meson-python-native-file.ini
      The Meson build system
      Version: 1.6.1
      Source dir: /tmp/pip-install-_qx6zrjm/pyshtools_a29c52ebf9ee40809aa559b8f9a4386d
      Build dir: /tmp/pip-install-_qx6zrjm/pyshtools_a29c52ebf9ee40809aa559b8f9a4386d/.mesonpy-szpr5sls
      Build type: native build
      Program python3 found: YES (/data/homes/jluethi/miniconda3/envs/scmultiplex-test/bin/python3)
      WARNING: You should add the boolean check kwarg to the run_command call.
               It currently defaults to false,
               but it will default to true in meson 2.0.
               See also: https://github.com/mesonbuild/meson/issues/9300
      Project name: shtools
      Project version: 4.13.1
      Fortran compiler for the host machine: gfortran (gcc 5.4.0 "GNU Fortran (Ubuntu 5.4.0-6ubuntu1~16.04.11) 5.4.0 20160609")
      Fortran linker for the host machine: gfortran ld.bfd 2.26.1
      C compiler for the host machine: cc (gcc 5.4.0 "cc (Ubuntu 5.4.0-6ubuntu1~16.04.11) 5.4.0 20160609")
      C linker for the host machine: cc ld.bfd 2.26.1
      Host machine cpu family: x86_64
      Host machine cpu: x86_64
      Found pkg-config: YES (/usr/bin/pkg-config) 0.29.1
      Found CMake: /usr/bin/cmake (3.18.4)
      Run-time dependency openblas found: NO (tried pkgconfig and cmake)
      Run-time dependency openblas found: NO (tried pkgconfig and cmake)
      Run-time dependency blas found: YES
      Dependency openblas found: YES unknown (cached)
      Run-time dependency fftw3 found: NO (tried pkgconfig and cmake)
      
      ../src/meson.build:109:8: ERROR: Dependency "fftw3" not found, tried pkgconfig and cmake
      
      A full log can be found at /tmp/pip-install-_qx6zrjm/pyshtools_a29c52ebf9ee40809aa559b8f9a4386d/.mesonpy-szpr5sls/meson-logs/meson-log.txt
      [end of output]
  
  note: This error originates from a subprocess, and is likely not a problem with pip.
error: metadata-generation-failed

× Encountered error while generating package metadata.
╰─> See above for output.

note: This is an issue with the package mentioned above, not pip.
hint: See above for details.

I'll document here how we work around that for future reference.