restrore showing stderr on script success (#38177)

* restrore showing stderr on script success

accidentally removed during transition to plugin, with toggle for those
who prefer the quiet way

fixes #33776

* stderr display if no other errors capture first
* fixed issue with error encoding

lib/ansible/plugins/inventory/script.py

@@ -19,6 +19,16 @@ DOCUMENTATION = '''
              key: cache
         env:
            - name: ANSIBLE_INVENTORY_PLUGIN_SCRIPT_CACHE
+      always_show_stderr:
+        description: Toggle display of stderr even when script was successful
+        version_added: "2.6"
+        default: True
+        type: boolean
+        ini:
+           - section: inventory_plugin_script
+             key: always_show_stderr
+        env:
+           - name: ANSIBLE_INVENTORY_PLUGIN_SCRIPT_STDERR
     description:
         - The source provided must an executable that returns Ansible inventory JSON
         - The source must accept C(--list) and C(--host <hostname>) as arguments.
@@ -64,7 +74,7 @@ class InventoryModule(BaseInventoryPlugin, Cacheable):
                     initial_chars = inv_file.read(2)
                     if initial_chars.startswith(b'#!'):
                         shebang_present = True
-            except:
+            except Exception:
                 pass
 
             if not os.access(path, os.X_OK) and not shebang_present:
@@ -99,8 +109,7 @@ class InventoryModule(BaseInventoryPlugin, Cacheable):
                 if sp.returncode != 0:
                     raise AnsibleError("Inventory script (%s) had an execution error: %s " % (path, err))
 
-                # make sure script output is unicode so that json loader will output
+                # make sure script output is unicode so that json loader will output unicode strings itself
-                # unicode strings itself
                 try:
                     data = to_text(stdout, errors="strict")
                 except Exception as e:
@@ -111,6 +120,10 @@ class InventoryModule(BaseInventoryPlugin, Cacheable):
                 except Exception as e:
                     raise AnsibleError("failed to parse executable inventory script results from {0}: {1}\n{2}".format(path, to_native(e), err))
 
+                # if no other errors happened and you want to force displaying stderr, do so now
+                if err and self.get_option('always_show_stderr'):
+                    self.display.error(msg=to_text(err))
+
             processed = self._cache[cache_key]
             if not isinstance(processed, Mapping):
                 raise AnsibleError("failed to parse executable inventory script results from {0}: needs to be a json dict\n{1}".format(path, err))