error when signing with CLI command

[haumenphai]

Describe the bug
USB sign

To Reproduce
Run CLI Command:

do@laptop:~/my_projects/odoo-17$ /home/do/my_projects/odoo-17/venv3.10saas-odoo17/bin/python3.10 -m pyhanko sign addsig pkcs11 --lib /usr/lib/viettel-ca_v6.so   --cert-label "TRẦN NGỌC TÚ's Viettel-CA SHA2 Certificate" /home/do/Desktop/product.pdf /home/do/Desktop/signed.pdf
PKCS#11 user PIN: 
Traceback (most recent call last):
  File "/home/do/my_projects/odoo-17/venv3.10saas-odoo17/lib/python3.10/site-packages/pkcs11/types.py", line 324, in get_key
    key = next(iterator)
  File "pkcs11/_pkcs11.pyx", line 320, in pkcs11._pkcs11.SearchIter.__next__
StopIteration

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/usr/lib/python3.10/runpy.py", line 196, in _run_module_as_main
    return _run_code(code, main_globals, None,
  File "/usr/lib/python3.10/runpy.py", line 86, in _run_code
    exec(code, run_globals)
  File "/home/do/my_projects/odoo-17/venv3.10saas-odoo17/lib/python3.10/site-packages/pyhanko/__main__.py", line 9, in <module>
    launch()
  File "/home/do/my_projects/odoo-17/venv3.10saas-odoo17/lib/python3.10/site-packages/pyhanko/cli/__init__.py", line 12, in launch
    cli_root(prog_name='pyhanko')
  File "/home/do/my_projects/odoo-17/venv3.10saas-odoo17/lib/python3.10/site-packages/click/core.py", line 1157, in __call__
    return self.main(*args, **kwargs)
  File "/home/do/my_projects/odoo-17/venv3.10saas-odoo17/lib/python3.10/site-packages/click/core.py", line 1078, in main
    rv = self.invoke(ctx)
  File "/home/do/my_projects/odoo-17/venv3.10saas-odoo17/lib/python3.10/site-packages/click/core.py", line 1688, in invoke
    return _process_result(sub_ctx.command.invoke(sub_ctx))
  File "/home/do/my_projects/odoo-17/venv3.10saas-odoo17/lib/python3.10/site-packages/click/core.py", line 1688, in invoke
    return _process_result(sub_ctx.command.invoke(sub_ctx))
  File "/home/do/my_projects/odoo-17/venv3.10saas-odoo17/lib/python3.10/site-packages/click/core.py", line 1688, in invoke
    return _process_result(sub_ctx.command.invoke(sub_ctx))
  File "/home/do/my_projects/odoo-17/venv3.10saas-odoo17/lib/python3.10/site-packages/click/core.py", line 1434, in invoke
    return ctx.invoke(self.callback, **ctx.params)
  File "/home/do/my_projects/odoo-17/venv3.10saas-odoo17/lib/python3.10/site-packages/click/core.py", line 783, in invoke
    return __callback(*args, **kwargs)
  File "/home/do/my_projects/odoo-17/venv3.10saas-odoo17/lib/python3.10/site-packages/pyhanko/cli/commands/signing/plugin.py", line 132, in _callback
    _callback_logic(plugin, infile, outfile, **kwargs)
  File "/home/do/my_projects/odoo-17/venv3.10saas-odoo17/lib/python3.10/site-packages/pyhanko/cli/commands/signing/plugin.py", line 111, in _callback_logic
    result = PdfSigner(
  File "/home/do/my_projects/odoo-17/venv3.10saas-odoo17/lib/python3.10/site-packages/pyhanko/sign/signers/pdf_signer.py", line 1078, in __init__
    mech = self.signer.get_signature_mechanism_for_digest(None)
  File "/home/do/my_projects/odoo-17/venv3.10saas-odoo17/lib/python3.10/site-packages/pyhanko/sign/signers/pdf_cms.py", line 400, in get_signature_mechanism_for_digest
    if self.signing_cert is None:
  File "/home/do/my_projects/odoo-17/venv3.10saas-odoo17/lib/python3.10/site-packages/pyhanko/sign/pkcs11.py", line 559, in signing_cert
    self._load_objects()
  File "/home/do/my_projects/odoo-17/venv3.10saas-odoo17/lib/python3.10/site-packages/pyhanko/sign/pkcs11.py", line 675, in _load_objects
    kh = self.pkcs11_session.get_key(
  File "/home/do/my_projects/odoo-17/venv3.10saas-odoo17/lib/python3.10/site-packages/pkcs11/types.py", line 326, in get_key
    raise NoSuchKey("No key matching %s" % attrs)
pkcs11.exceptions.NoSuchKey: No key matching {<Attribute.CLASS>: <ObjectClass.PRIVATE_KEY>, <Attribute.LABEL>: "TRẦN NGỌC TÚ's Viettel-CA SHA2 Certificate"}

Screenshots
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Environment (please complete the following information):

• OS: Ubuntu 20.04
• Python3.10