Adding a hyphen in the perms pattern section, since doing something like

go=- is a quick way to strip all permissions for non-owners.

lib/ansible/module_utils/basic.py

@@ -929,7 +929,7 @@ class AnsibleModule(object):
     def _symbolic_mode_to_octal(self, path_stat, symbolic_mode):
         new_mode = stat.S_IMODE(path_stat.st_mode)
 
-        mode_re = re.compile(r'^(?P<users>[ugoa]+)(?P<operator>[-+=])(?P<perms>[rwxXst]*|[ugo])$')
+        mode_re = re.compile(r'^(?P<users>[ugoa]+)(?P<operator>[-+=])(?P<perms>[rwxXst-]*|[ugo])$')
         for mode in symbolic_mode.split(','):
             match = mode_re.match(mode)
             if match: