[BUG] gpg modules crash/fail when GNUPGHOME does not exist

[lkubb]

Description
The gpg execution module crashes when GNUPGHOME does not exist (which also makes the state module fail).

Note: When invoking the gpg binary, it does work if the parent directory exists.

Setup
Irrelevant

Steps to Reproduce the behavior

• salt-call gpg.list_keys gnupghome=/tmp/tmpgnu

Expected behavior
Returns an empty list.

Screenshots

Traceback (most recent call last):
  File "/bin/salt-call", line 11, in <module>
    sys.exit(salt_call())
  File "/opt/saltstack/salt/lib/python3.10/site-packages/salt/scripts.py", line 443, in salt_call
    client.run()
  File "/opt/saltstack/salt/lib/python3.10/site-packages/salt/cli/call.py", line 50, in run
    caller.run()
  File "/opt/saltstack/salt/lib/python3.10/site-packages/salt/cli/caller.py", line 95, in run
    ret = self.call()
  File "/opt/saltstack/salt/lib/python3.10/site-packages/salt/cli/caller.py", line 202, in call
    ret["return"] = self.minion.executors[fname](
  File "/opt/saltstack/salt/lib/python3.10/site-packages/salt/loader/lazy.py", line 159, in __call__
    ret = self.loader.run(run_func, *args, **kwargs)
  File "/opt/saltstack/salt/lib/python3.10/site-packages/salt/loader/lazy.py", line 1251, in run
    return self._last_context.run(self._run_as, _func_or_method, *args, **kwargs)
  File "/opt/saltstack/salt/lib/python3.10/site-packages/salt/loader/lazy.py", line 1266, in _run_as
    return _func_or_method(*args, **kwargs)
  File "/opt/saltstack/salt/lib/python3.10/site-packages/salt/executors/direct_call.py", line 10, in execute
    return func(*args, **kwargs)
  File "/opt/saltstack/salt/lib/python3.10/site-packages/salt/loader/lazy.py", line 159, in __call__
    ret = self.loader.run(run_func, *args, **kwargs)
  File "/opt/saltstack/salt/lib/python3.10/site-packages/salt/loader/lazy.py", line 1251, in run
    return self._last_context.run(self._run_as, _func_or_method, *args, **kwargs)
  File "/opt/saltstack/salt/lib/python3.10/site-packages/salt/loader/lazy.py", line 1266, in _run_as
    return _func_or_method(*args, **kwargs)
  File "/opt/saltstack/salt/lib/python3.10/site-packages/salt/modules/gpg.py", line 284, in list_keys
    for _key in _list_keys(user, gnupghome):
  File "/opt/saltstack/salt/lib/python3.10/site-packages/salt/modules/gpg.py", line 196, in _list_keys
    gpg = _create_gpg(user, gnupghome)
  File "/opt/saltstack/salt/lib/python3.10/site-packages/salt/modules/gpg.py", line 187, in _create_gpg
    gpg = gnupg.GPG(gnupghome=gnupghome)
  File "/opt/saltstack/salt/extras-3.10/gnupg.py", line 854, in __init__
    raise ValueError('gnupghome should be a directory (it isn\'t): %s' % gnupghome)
ValueError: gnupghome should be a directory (it isn't): /tmp/tmpgnu

Versions Report

salt --versions-report

(Provided by running salt --versions-report. Please also mention any differences in master/minion versions.)

Salt Version:
          Salt: 3006.7

Python Version:
        Python: 3.10.13 (main, Feb 19 2024, 03:31:20) [GCC 11.2.0]

Dependency Versions:
          cffi: 1.14.6
      cherrypy: unknown
      dateutil: 2.8.1
     docker-py: Not Installed
         gitdb: 4.0.11
     gitpython: 3.1.42
        Jinja2: 3.1.3
       libgit2: Not Installed
  looseversion: 1.0.2
      M2Crypto: Not Installed
          Mako: Not Installed
       msgpack: 1.0.2
  msgpack-pure: Not Installed
  mysql-python: Not Installed
     packaging: 22.0
     pycparser: 2.21
      pycrypto: Not Installed
  pycryptodome: 3.19.1
        pygit2: Not Installed
  python-gnupg: 0.4.8
        PyYAML: 6.0.1
         PyZMQ: 23.2.0
        relenv: 0.15.1
         smmap: 5.0.1
       timelib: 0.2.4
       Tornado: 4.5.3
           ZMQ: 4.3.4

System Versions:
          dist: rocky 9.3 Blue Onyx
        locale: utf-8
       machine: x86_64
       release: 5.14.0-362.13.1.el9_3.x86_64
        system: Linux
       version: Rocky Linux 9.3 Blue Onyx

Additional context
I will submit a PR