Remove Python 3.6 CI tests

Author: Jürgen Hasch

appveyor.yml

@@ -13,13 +13,6 @@ environment:
     # appropriate libxml headers. As a result, make pip use binary packages.
     PIP_ONLY_BINARY: lxml
   matrix:
-
-    - TOXENV: 'py36-notebook60'
-      TOXPYTHON: C:\Python36\python.exe
-      PYTHON_HOME: C:\Python36
-      PYTHON_VERSION: '3.6'
-      PYTHON_ARCH: '64'
-
     - TOXENV: 'py37-notebook60'
       TOXPYTHON: C:\Python36\python.exe
       PYTHON_HOME: C:\Python37

tox.ini

@@ -6,21 +6,20 @@ envlist =
     clean,
     check,
     lint,
-    {py36,py37,py38}-notebook{60,63},
+    {py37,py38}-notebook{60,63},
     report,
 
 [testenv]
 basepython =
     pypy: {env:TOXPYTHON:pypy}
-    py36: {env:TOXPYTHON:python3.6}
     py37: {env:TOXPYTHON:python3.7}
     py38: {env:TOXPYTHON:python3.8}
     {spell}: {env:TOXPYTHON:python3.8}
-    {appveyorartifacts,lint,check}: {env:TOXPYTHON:python3}
+    {appveyorartifacts,lint,check}: {env:TOXPYTHON:python3.8}
     {condarecipe}: {env:TOXPYTHON:python3}
-    {clean,codecov,coveralls,report}: {env:TOXPYTHON:python3}
-    {docs,docs_build,docs_linkcheck}: {env:TOXPYTHON:python3}
-    {bump,pypi_build,pypi_upload}: {env:TOXPYTHON:python3}
+    {clean,codecov,coveralls,report}: {env:TOXPYTHON:python3.8}
+    {docs,docs_build,docs_linkcheck}: {env:TOXPYTHON:python3.8}
+    {bump,pypi_build,pypi_upload}: {env:TOXPYTHON:python3.8}
 setenv =
     PYTHONPATH={toxinidir}/tests
     PYTHONUNBUFFERED=yes