SolverProblemError when installing aiohttp

• 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: Lubuntu 18.04
• Poetry version: 0.11.1
• Link of a Gist with the contents of your pyproject.toml file: https://gist.github.com/Victor-Savu/e26e28cffd506bc399b5e0fae19dee62

Issue

Poetry incorrectly identifies idna-ssl to be a dependency of aiohttp when the required python is 3.7. Here is the result of poetry lock -vvv.

Here is a Dockerfile which can be used together with the linked pyproject.toml file to reproduce the error:

FROM python:3.7.0b5-alpine
RUN apk add --no-cache curl \
 && curl -sSL https://raw.githubusercontent.com/sdispater/poetry/master/get-poetry.py | python3
ADD pyproject.toml .
RUN poetry lock -vvv

The setup.py of aiohttp only includes the dependency on idna-ssl for versions lower than 3.7:

if sys.version_info < (3, 7):
    install_requires.append('idna-ssl>=1.0')

install_requires is later on passed to setuptools.setup(...).

idna-ssl indeed only supports python versions <3.7 but it should not be included as a dependency to begin with.

[Yanpas]

Had a problem with multidict:

 $ poetry update
Updating dependencies
Resolving dependencies... (0.2s)


Package operations: 7 installs, 0 updates, 0 removals

Writing lock file

  - Installing multidict (4.5.2)

[EnvCommandError]
Command ['pip', 'install', '--no-deps', 'multidict==4.5.2'] errored with
the following output:
Collecting multidict==4.5.2
  Could not find a version that satisfies the requirement multidict==4.5.
2 (from versions: 1.0.0a0, 1.0.1, 1.0.2, 1.0.3, 1.1.0b1, 1.1.0b2, 1.1.0b4
, 1.1.0b5, 1.1.0b6, 1.1.0b7, 1.1.0b8, 1.1.0, 1.2.0, 1.2.1, 1.2.2, 2.0.0,
2.0.1, 2.1.0, 2.1.1, 2.1.2, 2.1.3, 2.1.4, 2.1.5, 2.1.6, 3.0.0, 3.1.0, 3.1
.1, 3.1.3a0, 3.1.3, 3.1.4a1, 3.1.4a2, 3.1.4a3, 3.2.0a3, 3.2.0, 3.2.1a0, 3
.3.0, 3.3.1)
No matching distribution found for multidict==4.5.2

After rm -rf ~/.cache/pypoetry/ the error is gone.

toml file is simple:

[tool.poetry]
name = "xxx"
version = "0.1.0"
description = ""

[tool.poetry.dependencies]
python = "^3.6"
peewee = "^3.8"
aiohttp = "~3.5"

[tool.poetry.dev-dependencies]
pytest = "^3.0"

[build-system]
requires = ["poetry>=0.12"]
build-backend = "poetry.masonry.api"

[sdispater]

And it seems someone already opened a PR: https://github.com/aio-libs/aiohttp/pull/3114