Report detailed error when internal remote functions fail

This is a redesign in how plugins call _remote_checksum().

- _remote_stat() has been modified to report the real error as
  AnsiblError
- Action plugin **unarchive** calls _remote_stat() directly instead of
   _remote_checksum()
- Action plugin **unarchive** also handles the exceptions directly
- Ensure get_exception() returns native text

Two other action plugins, **template** and **fetch**, also do a remote checksum.
In **template** we already call _remote_stat(), just like we now do for
unarchive, in **fetch** we do call _remote_checksum() and we make the
exact same mistake as the unarchive plugin. So that one could use a
redesign as well.

This fixes #19494

Before:
```
[dag@moria ansible.testing]$ ansible-playbook -v test137.yml
Using /home/dag/home-made/ansible.testing/ansible.cfg as config file

PLAY [localhost]
******************************************************************************************************

TASK [unarchive]
******************************************************************************************************
fatal: [localhost]: FAILED! => {"changed": false, "failed": true, "msg":
"python isn't present on the system.  Unable to compute checksum"}

PLAY RECAP
******************************************************************************************************
localhost                  : ok=0    changed=0    unreachable=0
failed=1
```

After:
```
[dag@moria ansible.testing]$ ansible-playbook -v test137.yml
Using /home/dag/home-made/ansible.testing/ansible.cfg as config file

PLAY [localhost]
*************************************************************************************************************

TASK [unarchive]
*************************************************************************************************************
fatal: [localhost]: FAILED! => {"changed": false, "failed": true, "msg":
"Failed to get information on remote file (/tmp/): sudo: unknown user:
foobar\nsudo: unable to initialize policy plugin\n"}

PLAY RECAP
*******************************************************************************************************************
localhost                  : ok=0    changed=0    unreachable=0
failed=1
```

lib/ansible/plugins/action/__init__.py

@@ -443,8 +443,13 @@ class ActionBase(with_metaclass(ABCMeta, object)):
         )
         mystat = self._execute_module(module_name='stat', module_args=module_args, task_vars=all_vars, tmp=tmp, delete_remote_tmp=(tmp is None))
 
-        if 'failed' in mystat and mystat['failed']:
-            raise AnsibleError('Failed to get information on remote file (%s): %s' % (path, mystat['msg']))
+        if mystat.get('failed'):
+            msg = mystat.get('module_stderr')
+            if not msg:
+              msg = mystat.get('module_stdout')
+            if not msg:
+              msg = mystat.get('msg')
+            raise AnsibleError('Failed to get information on remote file (%s): %s' % (path, msg))
 
         if not mystat['stat']['exists']:
             # empty might be matched, 1 should never match, also backwards compatible

lib/ansible/plugins/action/template.py

@@ -25,6 +25,7 @@ import time
 from ansible import constants as C
 from ansible.errors import AnsibleError
 from ansible.module_utils._text import to_bytes, to_native, to_text
+from ansible.module_utils.pycompat24 import get_exception
 from ansible.plugins.action import ActionBase
 from ansible.utils.hashing import checksum_s
 
@@ -43,8 +44,8 @@ class ActionModule(ActionBase):
                 dest = os.path.join(dest, base)
                 dest_stat = self._execute_remote_stat(dest, all_vars=all_vars, follow=False, tmp=tmp)
 
-        except Exception as e:
-            return dict(failed=True, msg=to_bytes(e))
+        except AnsibleError:
+            return dict(failed=True, msg=to_native(get_exception()))
 
         return dest_stat['checksum']
 
@@ -69,9 +70,9 @@ class ActionModule(ActionBase):
         else:
             try:
                 source = self._find_needle('templates', source)
-            except AnsibleError as e:
+            except AnsibleError:
                 result['failed'] = True
-                result['msg'] = to_native(e)
+                result['msg'] = to_native(get_exception())
 
         if 'failed' in result:
             return result

lib/ansible/plugins/action/unarchive.py

@@ -22,6 +22,7 @@ import os
 
 from ansible.errors import AnsibleError
 from ansible.module_utils._text import to_native
+from ansible.module_utils.pycompat24 import get_exception
 from ansible.plugins.action import ActionBase
 from ansible.constants import mk_boolean as boolean
 
@@ -79,19 +80,21 @@ class ActionModule(ActionBase):
         if not remote_src:
             try:
                 source = self._loader.get_real_file(self._find_needle('files', source))
-            except AnsibleError as e:
+            except AnsibleError:
                 result['failed'] = True
-                result['msg'] = to_native(e)
+                result['msg'] = to_native(get_exception())
                 self._remove_tmp_path(tmp)
                 return result
 
-        remote_checksum = self._remote_checksum(dest, all_vars=task_vars, follow=True)
-        if remote_checksum == '4':
+        try:
+            remote_stat = self._execute_remote_stat(dest, all_vars=task_vars, follow=True)
+        except AnsibleError:
             result['failed'] = True
-            result['msg'] = "python isn't present on the system.  Unable to compute checksum"
+            result['msg'] = to_native(get_exception())
             self._remove_tmp_path(tmp)
             return result
-        elif remote_checksum != '3':
+
+        if not remote_stat['exists'] or not remote_stat['isdir']:
             result['failed'] = True
             result['msg'] = "dest '%s' must be an existing dir" % dest
             self._remove_tmp_path(tmp)