No module named '_cffi_backend' error

[akshaybabloo]

For some reason I am getting the following error:

Traceback (most recent call last):
  File "C:/Users/aksha/Documents/GitHub/neucube-cloud-api/temp.py", line 2, in <module>
    from azure.keyvault import KeyVaultClient, KeyVaultAuthentication
  File "C:\Users\aksha\Miniconda3\envs\neucube\lib\site-packages\azure\keyvault\__init__.py", line 15, in <module>
    from .key_vault_authentication import KeyVaultAuthentication, KeyVaultAuthBase, AccessToken
  File "C:\Users\aksha\Miniconda3\envs\neucube\lib\site-packages\azure\keyvault\key_vault_authentication.py", line 13, in <module>
    from azure.keyvault.http_message_security import HttpMessageSecurity
  File "C:\Users\aksha\Miniconda3\envs\neucube\lib\site-packages\azure\keyvault\http_message_security.py", line 9, in <module>
    from ._internal import _a128cbc_hs256_encrypt, _a128cbc_hs256_decrypt, _JwsHeader, _JwsObject, \
  File "C:\Users\aksha\Miniconda3\envs\neucube\lib\site-packages\azure\keyvault\_internal.py", line 16, in <module>
    from cryptography.hazmat.primitives import hashes, constant_time, padding, hmac
  File "C:\Users\aksha\Miniconda3\envs\neucube\lib\site-packages\cryptography\hazmat\primitives\constant_time.py", line 11, in <module>
    from cryptography.hazmat.bindings._constant_time import lib
ModuleNotFoundError: No module named '_cffi_backend'

This never happened, I am not sure what the problem is.

Versions

Python: 3.7
cryptography: 2.3.1
ciffi: 1.11.5
pip: 10.0.1
setuptools: 40.0.0

[reaperhulk]

This error typically occurs when something is wrong with your installation of cffi or it can't find it in the sys.path. I have no idea how anaconda/miniconda manage this, but you might try seeing if the problem exists if you install everything into a new virtualenv.

[akshaybabloo]

True. My bad. Seems to be a problem when upgrading python 3.6 to 3.7.

[orihomie]

True. My bad. Seems to be a problem when upgrading python 3.6 to 3.7.

So, how did u resolved this problem?

[akshaybabloo]

Downgrade to 3.6 for now. Till they add support for 3.7

[reaperhulk]

We support Python 3.7 (and indeed test against it in numerous configurations on 3 different OSes). This issue is not caused by a bug in cryptography or cffi and is almost always a problem with the environment on the user's machine. For instance, keeping the same packages while upgrading from 3.6 to 3.7 would break cffi (and any other C package that depends on version specific interfaces). You need to install cffi again with a 3.7 compatible version (which can be accomplished with pip install -U cffi).