fix setup.py python version

Author: timvink

setup.py

@@ -14,7 +14,7 @@
     author="Tim Vink",
     author_email="vinktim@gmail.com",
     license="MIT",
-    python_requires=">=3.6",
+    python_requires=">=3.8",
     classifiers=[
         "Operating System :: OS Independent",
         "Programming Language :: Python",