Refactor to use ixmp4 #152

	# This workflow runs the tests with the oldest explicitly supported versions of dependencies
	# For more information see: https://help.github.com/actions/language-and-framework-guides/using-python-with-github-actions

	name: pytest-legacy

	on:
	push:
	branches: [ 'main' ]
	pull_request:
	branches: [ '**' ]

	jobs:
	pytest-legacy:

	runs-on: ubuntu-latest

	steps:
	- uses: actions/checkout@v3

	- name: Set up Python
	uses: actions/setup-python@v4
	with:
	python-version: '3.8'

	- name: Install specific out-dated version of dependencies
	# Update the package requirements when changing minimum dependency versions
	# Please also add a section "Dependency changes" to the release notes
	run: pip install pandas==1.2.0 numpy==1.19.0 matplotlib==3.5.0 iam-units==2020.4.21 xlrd==2.0 pint==0.13

	- name: Install other dependencies and package
	run: pip install .[tests,optional_plotting,optional_io_formats,tutorials]

	- name: Test with pytest
	run: pytest tests

Provide feedback