# python gpgme-pytest.py 
!! testing encryption
Traceback (most recent call last):
  File "/usr/lib64/python3.4/site-packages/gpg/core.py", line 259, in encrypt
    self.op_encrypt_sign(recipients, flags, plaintext, ciphertext)
  File "/usr/lib64/python3.4/site-packages/gpg/core.py", line 151, in wrapper
    return _funcwrap(self, *args)
  File "/usr/lib64/python3.4/site-packages/gpg/core.py", line 135, in
_funcwrap
    return errorcheck(result, "Invocation of " + name)
  File "/usr/lib64/python3.4/site-packages/gpg/errors.py", line 62, in
errorcheck
    raise GPGMEError(retval, extradata)
gpg.errors.GPGMEError: Invocation of gpgme_op_encrypt_sign: GPGME: Unusable
secret key

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "gpgme-pytest.py", line 7, in <module>
    ciphertext, _, _ = c.encrypt(b"Hello world")
  File "/usr/lib64/python3.4/site-packages/gpg/core.py", line 263, in encrypt
    if e.getcode() == errors.UNUSABLE_PUBKEY:
AttributeError: 'module' object has no attribute 'UNUSABLE_PUBKEY'