Fix pip install and pysimple backend runtime

pyproject.toml

@@ -1,22 +1,18 @@
 [build-system]
-requires = ["scikit-build-core", "numpy", "f90wrap==0.2.16"]
+requires = ["scikit-build-core", "numpy", "f90wrap"]
 build-backend = "scikit_build_core.build"
 
 [project]
 name = "pysimple"
 version = "1.2.0"
-dependencies = ["numpy"]
+dependencies = ["numpy", "f90wrap"]
 classifiers = [
     "License :: OSI Approved :: MIT License",
 ]
 
 [tool.scikit-build]
-build-dir = "build"
 build.verbose = true
-cmake.define.CMAKE_CACHE_DIR = "build"
+build-dir = "_skbuild"
 wheel.packages = ["python/pysimple"]
-wheel.install-dir = "pysimple"
-wheel.exclude = []
-
-[project.package-data]
-pysimple = ["data/*.dat"]
+wheel.exclude = ["**/__pycache__/**", "**/*.pyc"]
+sdist.include = ["python/pysimple/data/*.dat"]

python/pysimple/__init__.py

@@ -22,6 +22,15 @@
 try:
     import simple_backend as _backend
 except ImportError as exc:
+    if getattr(exc, "name", None) == "f90wrap":
+        raise ImportError(
+            "f90wrap is required to import SIMPLE Python bindings. Install f90wrap."
+        ) from exc
+    if getattr(exc, "name", None) == "_simple_backend":
+        raise ImportError(
+            "Fortran extension _simple_backend failed to import. "
+            "Rebuild SIMPLE with Python bindings enabled."
+        ) from exc
     raise ImportError(
         "simple_backend module not found. Build SIMPLE with Python bindings enabled."
     ) from exc

python/pysimple/_backend.py

@@ -32,6 +32,15 @@ def _load_backend() -> ModuleType:
         try:
             _BACKEND = import_module("simple_backend")
         except ImportError as exc:  # pragma: no cover - exercised in test skips
+            if getattr(exc, "name", None) == "f90wrap":
+                raise ImportError(
+                    "f90wrap is required to import SIMPLE Python bindings. Install f90wrap."
+                ) from exc
+            if getattr(exc, "name", None) == "_simple_backend":
+                raise ImportError(
+                    "Fortran extension _simple_backend failed to import. "
+                    "Rebuild SIMPLE with Python bindings enabled."
+                ) from exc
             raise ImportError(
                 "simple_backend module not found. Build SIMPLE with Python bindings enabled."
             ) from exc