[ansiballz] ensure that '' is not in sys.path (#69342)

Change:
On OpenBSD when using pipelining, we do not set cwd which results in a
permissions fatal. Ensure that `''` - cwd - is not in `sys.path`.

Test Plan:
Tested against local OpenBSD VM

Tickets:
Fixes #69320

Signed-off-by: Rick Elrod <rick@elrod.me>

changelogs/fragments/69320-sys-path-cwd.yml

@@ -0,0 +1,2 @@
+bugfixes:
+  - ansiballz - remove '' and '.' from sys.path to fix a permissions issue on OpenBSD with pipelining (#69320)

docs/docsite/rst/porting_guides/porting_guide_2.10.rst

@@ -138,6 +138,7 @@ Noteworthy module changes
 * The parameter ``message`` in :ref:`grafana_dashboard <grafana_dashboard_module>` module is renamed to ``commit_message`` since ``message`` is used by Ansible Core engine internally.
 * The parameter ``message`` in :ref:`datadog_monitor <datadog_monitor_module>` module is renamed to ``notification_message`` since ``message`` is used by Ansible Core engine internally.
 * The parameter ``message`` in :ref:`bigpanda <bigpanda_module>` module is renamed to ``deployment_message`` since ``message`` is used by Ansible Core engine internally.
+* Ansible no longer looks for Python modules in the current working directory (typically the ``remote_user``'s home directory) when an Ansible module is run. This is to fix becoming an unprivileged user on OpenBSD and to mitigate any attack vector if the current working directory is writable by a malicious user. Install any Python modules needed to run the Ansible modules on the managed node in a system-wide location or in another directory which is in the ``remote_user``'s ``$PYTHONPATH`` and readable by the ``become_user``.
 
 
 Plugins

lib/ansible/executor/module_common.py

@@ -143,8 +143,10 @@ def _ansiballz_main():
         # OSX raises OSError if using abspath() in a directory we don't have
         # permission to read (realpath calls abspath)
         pass
-    if scriptdir is not None:
+
-        sys.path = [p for p in sys.path if p != scriptdir]
+    # Strip cwd from sys.path to avoid potential permissions issues
+    excludes = set(('', '.', scriptdir))
+    sys.path = [p for p in sys.path if p not in excludes]
 
     import base64
     import runpy