• 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: macOS 10.14.6 / docker image python:3.5
• Poetry version: 1.0.0
• Link of a Gist repository with the contents of your pyproject.toml file: https://github.com/ocavue/poetry_issue_celery

Issue

The steps to reproduce this bug is in the readme.

In short, I can't install any package with a custom pypi source (https://pypi.douban.com/simple/). pip3 install celery -i https://pypi.douban.com/simple/ works find, so this should be a bug of poetry.