poetry: Pip-installed Poetry encountering EnvironmentError "Permission denied" on Windows when upgrading cffi

• I am on the latest Poetry version.

• I have searched the issues of this repo and believe that this is not a duplicate.

• If an exception occurs when executing a command, I executed it again in debug mode (-vvv option).

• OS version and name: Windows 10

• Poetry version: 1.0.10

Issue

I’ve just encountered this problem while running poetry update, which upgraded the cffi package. Using pip 20.2.3 on python 3.9b5 on Windows 10, while using poetry 1.0.10.

PS C:\pas\projects\xxxx\ci> .\venv-windows\Scripts\python.exe -m poetry update
Skipping virtualenv creation, as specified in config file.
Updating dependencies
Resolving dependencies...

Writing lock file


Package operations: 0 installs, 5 updates, 0 removals

  - Updating attrs (19.3.0 -> 20.2.0)
  - Updating cffi (1.14.0 -> 1.14.2)

[EnvCommandError]
Command ['C:\\pas\\projects\\xxxx\\ci\\venv-windows\\Scripts\\python.exe', '-m', 'pip', 'install', '--no-deps', '-U', 'cffi==1.14.2'] errored with the following return code 1, and output:
Collecting cffi==1.14.2
  Downloading cffi-1.14.2.tar.gz (470 kB)
Using legacy 'setup.py install' for cffi, since package 'wheel' is not installed.
Installing collected packages: cffi
  Attempting uninstall: cffi
    Found existing installation: cffi 1.14.0
    Uninstalling cffi-1.14.0:
      Successfully uninstalled cffi-1.14.0
    Running setup.py install for cffi: started
    Running setup.py install for cffi: finished with status 'done'
ERROR: Could not install packages due to an EnvironmentError: [WinError 5] Permission denied: 'C:\\Users\\Admin\\AppData\\Local\\Temp\\pip-uninstall-8rjju1cu\\_cffi_backend.cp39-win_amd64.pyd'

Of course it’s not the best practice to install poetry via pip. Maybe providing a command line argument to ignore these errors might be worth it?