• 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: 0.12.16
• Link of a Gist with the contents of your pyproject.toml file:

Issue

While investigating #1150, I noticed that when normalizing pre-release, dev is translated to alpha when PEP 440 qualifies these as distinct stages. Doing this will cause problems when installing packages that use both stages of development (which we do internally).