Update minimum python version

Author: saimn

setup.cfg

@@ -15,6 +15,7 @@ classifiers =
     Programming Language :: Python :: 3
     Programming Language :: Python :: 3.6
     Programming Language :: Python :: 3.7
+    Programming Language :: Python :: 3.8
     Programming Language :: Python :: Implementation :: CPython
     Topic :: Scientific/Engineering :: Astronomy
     Topic :: Scientific/Engineering :: Physics
@@ -23,7 +24,7 @@ classifiers =
 zip_safe = False
 include_package_data = True
 packages = find:
-python_requires = >=3.5
+python_requires = >=3.6
 setup_requires =
     setuptools_scm
 install_requires =

setup.py

@@ -2,7 +2,7 @@
 
 from setuptools import setup
 
-if sys.version_info < (3, 5):
-    raise Exception('python 3.5 or newer is required')
+if sys.version_info < (3, 6):
+    raise Exception('python 3.6 or newer is required')
 
 setup(use_scm_version=True)