Poetry fails in CI/CD with ERROR: In --require-hashes mode, all requirements must have their versions pinned

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- [x] I am on the [latest](https://github.com/python-poetry/poetry/releases/latest) Poetry version.

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- **OS version and name**: Ubuntu 18.04.5 LTS

- **Poetry version**: 1.1.4

- **Link of a [Gist](https://gist.github.com/) with the contents of your pyproject.toml file**: https://github.com/DontShaveTheYak/cloud-radar/pull/5



## Issue



My builds were working fine locally and remotely. Here is an example of the first 12 or so lines...



```sh

2020-11-28T13:25:00.7733264Z ##[group]Run nox

2020-11-28T13:25:00.7733666Z ^[[36;1mnox^[[0m

2020-11-28T13:25:00.7772013Z shell: /bin/bash -e {0}

2020-11-28T13:25:00.7772325Z env:

2020-11-28T13:25:00.7772772Z   pythonLocation: /opt/hostedtoolcache/Python/3.8.6/x64

2020-11-28T13:25:00.7773219Z ##[endgroup]

2020-11-28T13:25:00.8815564Z nox > Running session lint-3.9

2020-11-28T13:25:00.8867576Z nox > Session lint-3.9 skipped: Python interpreter 3.9 not found.

2020-11-28T13:25:00.8869448Z nox > Running session lint-3.8

2020-11-28T13:25:00.8870400Z nox > Creating virtual environment (virtualenv) using python3.8 in .nox/lint-3-8

2020-11-28T13:25:01.6319387Z nox > poetry export --dev --format=requirements.txt --output=/tmp/tmp2554a7nu

2020-11-28T13:25:04.4828117Z nox > pip install --constraint=/tmp/tmp2554a7nu flake8 flake8-black flake8-bugbear flake8-import-order

2020-11-28T13:25:11.0176722Z nox > flake8 src tests noxfile.py

```



I added a package with `poetry add cfn-flip`





My builds still work locally but fail in github actions:



```sh

2020-12-10T12:32:26.6270480Z ##[group]Run nox

2020-12-10T12:32:26.6270955Z ^[[36;1mnox^[[0m

2020-12-10T12:32:26.6313567Z shell: /bin/bash -e {0}

2020-12-10T12:32:26.6313932Z env:

2020-12-10T12:32:26.6314480Z   pythonLocation: /opt/hostedtoolcache/Python/3.8.6/x64

2020-12-10T12:32:26.6315036Z ##[endgroup]

2020-12-10T12:32:26.7301178Z nox > Running session lint-3.9

2020-12-10T12:32:26.7352891Z nox > Session lint-3.9 skipped: Python interpreter 3.9 not found.

2020-12-10T12:32:26.7354096Z nox > Running session lint-3.8

2020-12-10T12:32:26.7357585Z nox > Creating virtual environment (virtualenv) using python3.8 in .nox/lint-3-8

2020-12-10T12:32:27.5320470Z nox > poetry export --dev --format=requirements.txt --output=/tmp/tmp2k2e6e06

2020-12-10

[]