Add gpg_fingerprint lookup and filter (#639)

* Add gpg_fingerprint lookup.

* Work around problems on some CI targets.

* Use get_bin_path to find the gpg executable. Document that we need it.

* Improve and test error handling.

* Refactor (potentially) common code to module_utils and plugin_utils.

This will be useful to create a filter version of this, and further lookups, filters, and modules.

* Do not create a keyring when there isn't one.

* Fixups.

* Fix description.

* More fixes for lookup.

* Also add a gpg_fingerprint filter.

* Improve formulation.

Co-authored-by: Sandra McCann <samccann@redhat.com>

---------

Co-authored-by: Sandra McCann <samccann@redhat.com>

plugins/plugin_utils/gnupg.py

@@ -0,0 +1,51 @@
+# -*- coding: utf-8 -*-
+# Copyright (c) 2023, Felix Fontein <felix@fontein.de>
+# GNU General Public License v3.0+ (see LICENSES/GPL-3.0-or-later.txt or https://www.gnu.org/licenses/gpl-3.0.txt)
+# SPDX-License-Identifier: GPL-3.0-or-later
+
+from __future__ import (absolute_import, division, print_function)
+__metaclass__ = type
+
+from subprocess import Popen, PIPE
+
+from ansible.module_utils.common.process import get_bin_path
+from ansible.module_utils.common.text.converters import to_native
+
+from ansible_collections.community.crypto.plugins.module_utils.gnupg.cli import GPGError, GPGRunner
+
+
+class PluginGPGRunner(GPGRunner):
+    def __init__(self, executable=None, cwd=None):
+        if executable is None:
+            try:
+                executable = get_bin_path('gpg')
+            except ValueError as e:
+                raise GPGError('Cannot find the `gpg` executable on the controller')
+        self.executable = executable
+        self.cwd = cwd
+
+    def run_command(self, command, check_rc=True, data=None):
+        """
+        Run ``[gpg] + command`` and return ``(rc, stdout, stderr)``.
+
+        If ``data`` is not ``None``, it will be provided as stdin.
+        The code assumes it is a bytes string.
+
+        Returned stdout and stderr are native Python strings.
+        Pass ``check_rc=False`` to allow return codes != 0.
+
+        Raises a ``GPGError`` in case of errors.
+        """
+        command = [self.executable] + command
+        p = Popen(command, shell=False, cwd=self.cwd, stdin=PIPE, stdout=PIPE, stderr=PIPE)
+        stdout, stderr = p.communicate(input=data)
+        stdout = to_native(stdout, errors='surrogate_or_replace')
+        stderr = to_native(stderr, errors='surrogate_or_replace')
+        if check_rc and p.returncode != 0:
+            raise GPGError('Running {cmd} yielded return code {rc} with stdout: "{stdout}" and stderr: "{stderr}")'.format(
+                cmd=' '.join(command),
+                rc=p.returncode,
+                stdout=to_native(stdout, errors='surrogate_or_replace'),
+                stderr=to_native(stderr, errors='surrogate_or_replace'),
+            ))
+        return p.returncode, stdout, stderr