L2SS-627: Update minimal python version

In addition this patch prepares our tox.ini for tox version 4
by better preventing system wide binary access using tox built in
variables.

tangostationcontrol/setup.cfg

@@ -17,7 +17,6 @@ classifier =
     Operating System :: POSIX :: Linux
     Programming Language :: Python
     Programming Language :: Python :: 3
-    Programming Language :: Python :: 3.6
     Programming Language :: Python :: 3.7
     Programming Language :: Python :: 3.8
     Programming Language :: Python :: 3.9
@@ -27,7 +26,7 @@ classifier =
 package_dir=
     =./
 packages=find:
-python_requires = >=3.6
+python_requires = >=3.7
 
 [options.packages.find]
 where=./

tangostationcontrol/tox.ini

 [tox]
-minversion = 2.0
-envlist = py36,py37,py38,py39,py310,pep8
+minversion = 3.20
+envlist = py37,py38,py39,py310,pep8
 skipsdist = True
 
 [testenv]
 usedevelop = True
+; Module access is a bit of an ugly hack. This is due to testenv inheritance
+; with sitepackages = True`, meaning that global packages can be accessed by the
+; tox environment. Our tango images already have several dependencies system
+; wide installed, however, the system wide installation will never look inside
+; tox its virtualenv for packages. So accessing stestr and others fail.. We
+; can't remove `sitepackages = True` either as we need access to tango and
+; installing this package is non-trivial. The solution is to prevent calling
+; binaries directly and utilizing python and tox variables to resolve the
+; requested module.
 sitepackages = True
-install_command = pip3 install {opts} {packages}
+install_command = {envbindir}/pip3 install {opts} {packages}
 passenv = HOME
 setenv =
    VIRTUAL_ENV={envdir}
    PYTHONWARNINGS=default::DeprecationWarning
-   OS_STDOUT_CAPTURE=1
-   OS_STDERR_CAPTURE=1
-   OS_TEST_TIMEOUT=60
 deps =
     -r{toxinidir}/../docker-compose/lofar-device-base/lofar-requirements.txt
     -r{toxinidir}/test-requirements.txt
-commands = stestr run {posargs}
+commands = {envpython} -m stestr run {posargs}
 
 [testenv:integration]
 ; Warning running integration tests will make changes to your docker system!
@@ -25,39 +31,30 @@ commands = stestr run {posargs}
 passenv = TANGO_HOST
 setenv = TESTS_DIR=./tangostationcontrol/integration_test/{posargs}
 commands =
-    stestr run --serial
+    {envpython} -m stestr run --serial
 
-; The access to coverage as module is a bit of an ugly hack. This is due to
-; cover inheriting testenv which has `sitepackages = True`, meaning that global
-; packages can be accessed by the tox environment. Our tango images already have
-; coverage system wide installed, however, the system wide installation will
-; never look inside tox its virtualenv for packages. So accessing stestr and
-; others fail.. We can't remove `sitepackages = True` either as we need access
-; to tango and installing this package is non-trivial. The solution is to
-; prevent calling binaries directly and utilizing python to resolve the
-; requested module. In addition stestr does not natively support generating
-; coverage reports which is where the `PYTHON=python -m coverage run....` comes
-; from.
 [testenv:cover]
+; stestr does not natively support generating coverage reports use
+; `PYTHON=python -m coverage run....` to overcome this.
 setenv =
     VIRTUAL_ENV={envdir}
-    PYTHON=python -m coverage run --source tangostationcontrol --parallel-mode
+    PYTHON={envpython} -m coverage run --source tangostationcontrol --parallel-mode
 deps =
-    -r{toxinidir}/test-requirements.txt
     -r{toxinidir}/../docker-compose/lofar-device-base/lofar-requirements.txt
+    -r{toxinidir}/test-requirements.txt
 commands =
-  python -m coverage erase
-  stestr run {posargs}
-  python -m coverage combine
-  python -m coverage html -d cover
-  python -m coverage xml -o coverage.xml
-  python -m coverage report
+  {envpython} -m coverage erase
+  {envpython} -m stestr run {posargs}
+  {envpython} -m coverage combine
+  {envpython} -m coverage html -d cover
+  {envpython} -m coverage xml -o coverage.xml
+  {envpython} -m coverage report
 
 ; TODO(Corne): Integrate Hacking to customize pep8 rules
 [testenv:pep8]
 commands =
-    doc8 docs/source/ --ignore D001
-    flake8
+    {envpython} -m doc8 docs/source/ --ignore D001
+    {envpython} -m flake8
 
 [testenv:bandit];
 ; B104: hardcoded_bind_all_interfaces
@@ -65,11 +62,11 @@ commands =
 ;             It thus matters what interfaces Docker will bind our
 ;             containers to, not what our containers listen on.
 commands =
-    bandit -r devices/ -n5 -ll -s B104
+    {envpython} -m bandit -r devices/ -n5 -ll -s B104
 
 [testenv:xenon];
 commands =
-    xenon tangostationcontrol -b B -m A -a A
+     {envpython} -m xenon tangostationcontrol -b B -m A -a A
 
 [testenv:docs]
 deps =