Drop support for python 3.6 which is EOL

Author: philpep

.github/workflows/tox.yml

@@ -24,7 +24,6 @@ jobs:
         include:
           - tox_env: lint
           - tox_env: docs
-          - tox_env: py36
           - tox_env: py37
           - tox_env: py38
           - tox_env: py39
@@ -72,10 +71,10 @@ jobs:
       TOXENV: packaging
 
     steps:
-      - name: Switch to using Python 3.6 by default
+      - name: Switch to using Python 3.7 by default
         uses: actions/setup-python@v2
         with:
-          python-version: 3.6
+          python-version: 3.7
       - name: Install tox
         run: python -m pip install --user tox
       - name: Check out src from Git

pyproject.toml

@@ -1,5 +1,5 @@
 [tool.black]
-target-version = ['py36']
+target-version = ['py37']
 include = '\.pyi?$'
 exclude = '''
 (

setup.cfg

@@ -18,7 +18,6 @@ classifiers =
     Programming Language :: Python
     Programming Language :: Python :: 3
     Programming Language :: Python :: 3 :: Only
-    Programming Language :: Python :: 3.6
     Programming Language :: Python :: 3.7
     Programming Language :: Python :: 3.8
     Programming Language :: Python :: 3.9
@@ -29,7 +28,7 @@ classifiers =
 
 [options]
 use_scm_version = True
-python_requires = >=3.6
+python_requires = >=3.7
 packages = find:
 setup_requires =
     setuptools_scm