require Python 3.7

drops support for Python 3.6

pyproject.toml

@@ -6,7 +6,6 @@ skip-string-normalization = true
 # target-version should be all supported versions, see
 # https://github.com/psf/black/issues/751#issuecomment-473066811
 target_version = [
-    "py36",
     "py37",
     "py38",
     "py39",

setup.py

@@ -91,7 +91,7 @@ setup_args = dict(
     license="BSD",
     platforms="Linux, Mac OS X",
     keywords=['Interactive', 'Interpreter', 'Shell', 'Web'],
-    python_requires=">=3.6",
+    python_requires=">=3.7",
     entry_points={
         'jupyterhub.authenticators': [
             'default = jupyterhub.auth:PAMAuthenticator',