merge master into tox

this also removes the unsupported/untested Python versions

tox.ini

@@ -1,16 +1,15 @@
 # to run for a specific environment, use ``tox -e ENVNAME``
 [tox]
-envlist = py27,py36,py37,py38,py39,py310,pypy3
+envlist = py27,py37,py38,py39,py310,pypy3
 
 [testenv]
+usedevelop=True
 deps =
     pytest
     coverage
-    py{27,36}: hypothesis>=3.0
-extras =
-    test
+    py{27}: hypothesis>=3.0
 commands =
     coverage run --source=src/icalendar --omit=*/tests/* --module pytest []
-    py{27,36}: coverage run --append --source=src/icalendar --omit=*/tests/* --module pytest [] src/icalendar/tests/hypothesis/
+    py{27}: coverage run --append --source=src/icalendar --omit=*/tests/* --module pytest [] src/icalendar/tests/hypothesis/
     coverage report
     coverage html