Ensure that command/shell errors are displayed

This fix ensures that if there are specific module errors (in our case
the python interpreter was not found) then command and shell returns a
proper error.

It also fixes a few other imperfections that we noticed during
troubleshooting:

- Return the real RC if it were available
- Improve a dictionary evaluation using .get()
- Return an RC of -1 if it is unknown (instead of returning 0)

This fixes #18846

lib/ansible/plugins/callback/minimal.py

@@ -37,7 +37,7 @@ class CallbackModule(CallbackBase):
     def _command_generic_msg(self, host, result, caption):
         ''' output the result of a command run '''
 
-        buf = "%s | %s | rc=%s >>\n" % (host, caption, result.get('rc',0))
+        buf = "%s | %s | rc=%s >>\n" % (host, caption, result.get('rc', -1))
         buf += result.get('stdout','')
         buf += result.get('stderr','')
         buf += result.get('msg','')
@@ -55,7 +55,7 @@ class CallbackModule(CallbackBase):
 
             self._display.display(msg, color=C.COLOR_ERROR)
 
-        if result._task.action in C.MODULE_NO_JSON:
+        if result._task.action in C.MODULE_NO_JSON and 'module_stderr' not in result._result:
             self._display.display(self._command_generic_msg(result._host.get_name(), result._result, "FAILED"), color=C.COLOR_ERROR)
         else:
             self._display.display("%s | FAILED! => %s" % (result._host.get_name(), self._dump_results(result._result, indent=4)), color=C.COLOR_ERROR)