fix(macos): report permission error if not root

This change ensures that Austin reports the expected error code and
message when running without the superuser privileges.

src/austin.c

@@ -215,6 +215,15 @@ do_child_processes(py_proc_t * py_proc) {
 
 // ----------------------------------------------------------------------------
 int main(int argc, char ** argv) {
+
+#if defined PL_MACOS
+  // On MacOS, we need to be root to use Austin.
+  if (geteuid() != 0) {
+    _msg(MPERM);
+    return EPROCPERM;
+  }
+#endif
+
   int         retval         = 0;
   py_proc_t * py_proc        = NULL;
   int         exec_arg       = parse_args(argc, argv);

test/test_cli.py

@@ -70,3 +70,15 @@ def test_cli_permissions():
         result = austin("-i", "1ms", "-p", str(p.pid))
         assert result.returncode == 37, result.stderr
         assert "Insufficient permissions" in result.stderr, result.stderr
+
+
+@pytest.mark.skipif(
+    platform.system() != "Darwin",
+    reason="Only Darwing requires sudo in all cases",
+)
+def test_cli_permissions_darwin():
+        result = austin(
+            "-i", "1ms", "python3.10", "-c", "'from time import sleep; sleep(1)'"
+        )
+        assert result.returncode == 37, result.stderr
+        assert "Insufficient permissions" not in result.stderr, result.stderr