Rewrite nvjitlink_linux.pyx load_library() to produce detailed error messages.

Author: rwgk

cuda_bindings/cuda/bindings/_internal/nvjitlink_linux.pyx

@@ -65,20 +65,31 @@ cdef void* load_library(const int driver_ver) except* with gil:
     cdef void* handle = NULL;
     paths = path_finder.get_cuda_paths()
     paths_cudalib_dir = paths["cudalib_dir"]
-    if (paths_cudalib_dir and
-        paths_cudalib_dir.info and
-        os.path.isdir(paths_cudalib_dir.info)):
-        # TODO(rwgk): Produce the correct so_name in path_finder.py
-        so_name = os.path.join(paths_cudalib_dir.info, so_basename)
-        if not os.path.exists(so_name) and so_name.count("/lib64/") == 1:
-            so_name = so_name.replace("/lib64/", "/lib/")
-        if os.path.exists(so_name):
+    if not paths_cudalib_dir:
+        raise RuntimeError("Failure obtaining paths_cudalib_dir")
+    if not paths_cudalib_dir.info:
+        raise RuntimeError("Failure obtaining paths_cudalib_dir.info")
+    candidate_so_dirs = [paths_cudalib_dir.info]
+    libs = ["/lib/", "/lib64/"]
+    for _ in range(2):
+        alt_dir = libs[0].join(paths_cudalib_dir.info.rsplit(libs[1], 1))
+        if alt_dir not in candidate_so_dirs:
+            candidate_so_dirs.append(alt_dir)
+        libs.reverse()
+    candidate_so_names = [
+        os.path.join(so_dirname, so_basename)
+        for so_dirname in candidate_so_dirs]
+    error_messages = []
+    for so_name in candidate_so_names:
+        if not os.path.exists(so_name):
+            error_messages.append(f"No such file: {so_name}")
+        else:
             handle = dlopen(so_name.encode(), RTLD_NOW | RTLD_GLOBAL)
-            if handle == NULL:
-                err_msg = dlerror()
-                raise RuntimeError(f'Failed to dlopen {so_name} ({err_msg.decode()})')
-            return handle
-    raise RuntimeError(f'Unable to locate {so_basename}')
+            if handle != NULL:
+                return handle
+            err_msg = dlerror().decode(errors="backslashreplace")
+            error_messages.append(f"Failed to dlopen {so_name}: {err_msg}")
+    raise RuntimeError(f"Unable to load {so_basename}: {', '.join(error_messages)}")
 
 
 cdef int _check_or_init_nvjitlink() except -1 nogil: