Use shutil.which to find generator interpreters, as sometimes shutil.…

…which can find binaries that the system cannot. See Pythons Popen documentation.

fusesoc/capi2/json_schema.py

@@ -317,7 +317,7 @@
               "type": "string"
             },
             "interpreter": {
-              "description": "If the command needs a custom interpreter (such as python) this will be inserted as the first argument before command when calling the generator. The interpreter needs to be on the system PATH.",
+              "description": "If the command needs a custom interpreter (such as python) this will be inserted as the first argument before command when calling the generator. The interpreter needs to be on the system PATH; specifically, shutil.which needs to be able to find the interpreter).",
               "type": "string"
             },
             "cache_type": {

fusesoc/edalizer.py

@@ -521,6 +521,7 @@ def __init__(self, ttptttg, core, generators, gen_root, resolve_env_vars=False):
         self.generator = generators[generator_name]
         self.name = ttptttg["name"]
         self.pos = ttptttg["pos"]
+        self.gen_name = generator_name
         self.gen_root = gen_root
         self.resolve_env_vars = resolve_env_vars
         parameters = ttptttg["config"]
@@ -601,7 +602,14 @@ def _run(self, generator_cwd):
         ]
 
         if "interpreter" in self.generator:
-            args[0:0] = [self.generator["interpreter"]]
+            interp = self.generator["interpreter"]
+            interppath = shutil.which(interp)
+            if not interppath:
+                raise RuntimeError(
+                    f"Could not find generator interpreter '{interp}' using shutil.which.\n"
+                    f"Interpreter requested by generator {self.gen_name}, requested by core {self.core}.\n"
+                )
+            args[0:0] = [interppath]
 
         Launcher(args[0], args[1:], cwd=generator_cwd).run()