diff --git a/ansible_mitogen/helpers.py b/ansible_mitogen/helpers.py
index 2bd0b28c..25b091c8 100644
--- a/ansible_mitogen/helpers.py
+++ b/ansible_mitogen/helpers.py
@@ -289,7 +289,7 @@ def set_file_mode(path, spec):
     """
     mode = os.stat(path).st_mode
 
-    if spec.is_digit():
+    if spec.isdigit():
         new_mode = int(spec, 8)
     else:
         new_mode = apply_mode_spec(spec, mode)
diff --git a/ansible_mitogen/mixins.py b/ansible_mitogen/mixins.py
index db7dac18..9aa133c4 100644
--- a/ansible_mitogen/mixins.py
+++ b/ansible_mitogen/mixins.py
@@ -28,6 +28,7 @@
 
 from __future__ import absolute_import
 import commands
+import logging
 import os
 import pwd
 import shutil
@@ -52,6 +53,9 @@ import ansible_mitogen.helpers
 from ansible.module_utils._text import to_text
 
 
+LOG = logging.getLogger(__name__)
+
+
 def get_command_module_name(module_name):
     """
     Given the name of an Ansible command module, return its canonical module
@@ -157,6 +161,7 @@ class ActionModuleMixin(ansible.plugins.action.ActionBase):
             if stdout:
                 dct['stdout'] = repr(rc)
         except mitogen.core.CallError:
+            LOG.exception('While emulating a shell command')
             dct['rc'] = 1
             dct['stderr'] = traceback.format_exc()