packaging: Python tools use the system python not venv python

eris/tools.py

@@ -35,8 +35,7 @@ import tomllib
 import eris
 
 
-PYTHON_VERSION = "3.11"
-PYTHON_EXECUTABLE = "python" + PYTHON_VERSION
+PYTHON_EXECUTABLE = "/usr/bin/python3"
 CACHE_PATH = ".eris"
 
 
@@ -654,13 +653,16 @@ def splitext(path):
     return root, ext
 
 
+def python_has_module(python_path, module_name):
+    one_liner = ("import importlib, sys; "
+                 f"sys.exit(importlib.util.find_spec('{module_name}') is not None)")
+    return bool(subprocess.call([python_path, "-c", one_liner]))
+
+
 @functools.cache
 def is_tool_available(tool):
     if (hasattr(tool, "command") and tool.command.startswith(f"{PYTHON_EXECUTABLE} -m ")):
-        try:
-            return importlib.util.find_spec(tool.command.split()[2]) is not None
-        except ModuleNotFoundError:
-            return False
+        return python_has_module(PYTHON_EXECUTABLE, tool.command.split()[2])
     try:
         return all(shutil.which(executable) for executable in tool.executables)
     except AttributeError: