restrict project to Python 3.7 and 3.8 (#715)

Author: hotzenklotz

webknossos/pyproject.toml

@@ -10,7 +10,7 @@ homepage = "https://docs.webknossos.org/webknossos-py"
 include = ["webknossos/version.py"]  # included explicitly since it's in .gitignore
 
 [tool.poetry.dependencies]
-python = "^3.7,>=3.7.1"
+python = ">=3.7.1,<3.9"
 attrs = "^21.1.0"
 boltons = "~21.0.0"
 cattrs = "1.7.1"