Raise requirement to Python 3.8

bytes.hex(":") does not work before 3.8.

Author: schodet

setup.cfg

@@ -10,6 +10,10 @@ url = https://github.com/schodet/nxt-python/
 classifiers =
 	Programming Language :: Python :: 3
 	Programming Language :: Python :: 3 :: Only
+	Programming Language :: Python :: 3.8
+	Programming Language :: Python :: 3.9
+	Programming Language :: Python :: 3.10
+	Programming Language :: Python :: 3.11
 	License :: OSI Approved :: GNU General Public License v3 or later (GPLv3+)
 	Operating System :: OS Independent
 
@@ -24,7 +28,7 @@ scripts =
 	scripts/nxt_push
 	scripts/nxt_server
 	scripts/nxt_test
-python_requires = >=3.6
+python_requires = >=3.8
 install_requires =
 	pyusb >= 1.2.1
 	pybluez >= 0.23; platform_system == 'Linux'