config: relax poetry Python version

Allow older Python versions to support older CI configs.

poetry.lock

@@ -139,7 +139,7 @@ description = "Core utilities for Python packages"
 name = "packaging"
 optional = false
 python-versions = ">=2.7, !=3.0.*, !=3.1.*, !=3.2.*, !=3.3.*"
-version = "20.1"
+version = "20.3"
 
 [package.dependencies]
 pyparsing = ">=2.0.2"
@@ -325,8 +325,8 @@ secure = ["pyOpenSSL (>=0.14)", "cryptography (>=1.3.4)", "idna (>=2.0.0)", "cer
 socks = ["PySocks (>=1.5.6,<1.5.7 || >1.5.7,<2.0)"]
 
 [metadata]
-content-hash = "a27f499602c68e1c91bdcac83d0970225983bb122ec0b58591ed3dd3bda3a840"
-python-versions = "^3.6.8"
+content-hash = "cfdc758b3080a5936922c4ed5c24bb32b1d729927a10c6bfd7d0a915f6d2f88f"
+python-versions = "^3.5"
 
 [metadata.files]
 alabaster = [
@@ -417,8 +417,8 @@ mccabe = [
     {file = "mccabe-0.6.1.tar.gz", hash = "sha256:dd8d182285a0fe56bace7f45b5e7d1a6ebcbf524e8f3bd87eb0f125271b8831f"},
 ]
 packaging = [
-    {file = "packaging-20.1-py2.py3-none-any.whl", hash = "sha256:170748228214b70b672c581a3dd610ee51f733018650740e98c7df862a583f73"},
-    {file = "packaging-20.1.tar.gz", hash = "sha256:e665345f9eef0c621aa0bf2f8d78cf6d21904eef16a93f020240b704a57f1334"},
+    {file = "packaging-20.3-py2.py3-none-any.whl", hash = "sha256:82f77b9bee21c1bafbf35a84905d604d5d1223801d639cf3ed140bd651c08752"},
+    {file = "packaging-20.3.tar.gz", hash = "sha256:3c292b474fda1671ec57d46d739d072bfd495a4f51ad01a055121d81e952b7a3"},
 ]
 pbr = [
     {file = "pbr-5.4.4-py2.py3-none-any.whl", hash = "sha256:61aa52a0f18b71c5cc58232d2cf8f8d09cd67fcad60b742a60124cb8d6951488"},

pyproject.toml

@@ -6,7 +6,7 @@ authors = ["Laurens Valk <laurens@pybricks.com>", "David Lechner <david@pybricks
 license = "MIT"
 
 [tool.poetry.dependencies]
-python = "^3.6.8"
+python = "^3.5"
 sphinx = "==1.7.9"
 flake8 = "*"
 sphinx-rtd-theme = "==0.4.3"