Make min python version 3.8 (#208)

Jenkinsfile

@@ -3,7 +3,7 @@ if (utils.scm_checkout()) return
 
 // Define each build configuration, copying and overriding values as necessary.
 bc0 = new BuildConfig()
-bc0.nodetype = "python3.7"
+bc0.nodetype = "python3.8"
 bc0.name = "egg"
 bc0.build_cmds = ["pip install numpy",
                   "python setup.py egg_info"]
@@ -12,7 +12,7 @@ bc1 = utils.copy(bc0)
 bc1.name = "release"
 // Would be nice if Jenkins can access /grp/hst/cdbs/xxxx directly.
 bc1.env_vars = ['TEST_BIGDATA=https://bytesalad.stsci.edu/artifactory']
-// bc1.conda_packages = ['python=3.7',
+// bc1.conda_packages = ['python=3.8',
 //                      'requests',
 //                      'numpy',
 //                      'stsci.tools']

JenkinsfileRT

@@ -14,7 +14,7 @@ bc.name = "release"
 bc.env_vars = ['TEST_BIGDATA=https://bytesalad.stsci.edu/artifactory',
                'lref=/grp/hst/cdbs/lref/']
 bc.conda_channels = ['http://ssb.stsci.edu/astroconda']
-bc.conda_packages = ['python=3.7']
+bc.conda_packages = ['python=3.8']
 //                     'requests',
 //                     'numpy',
 //                     'stsci.tools']

setup.cfg

@@ -1,3 +1,6 @@
+[options]
+python_requires = >=3.8
+
 [tool:pytest]
 minversion = 3.0
 norecursedirs = build doc/build src