drop support for Python 2.x as it is very much EOL

[kartben]

A follow-up to b96a5ad where we stopped having CI run tests on Python 2.x. This actually drops the few remaining Python 2.x compatibility bits as Python 2.x has EOL'd a long time ago.

[tejlmand]

A couple of more places needs to be updated as well:

Kconfiglib/README.rst

Lines 124 to 126 in 1e6f644

	Starting with Kconfiglib version 12.2.0, all utilities are compatible with both
	Python 2 and Python 3. Previously, ``menuconfig.py`` only ran under Python 3
	(i.e., it's now more backwards compatible than before).

Kconfiglib/README.rst

Line 36 in 1e6f644

implementation in Python 2/3. It started out as a helper library, but now has a

Kconfiglib/README.rst

Lines 167 to 174 in 1e6f644

	Python version compatibility (2.7/3.2+)
	~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
	Kconfiglib and all utilities run under both Python 2.7 and Python 3.2 and
	later. The code mostly uses basic Python features and has no third-party
	dependencies, so keeping it backwards-compatible is pretty low effort.
	The 3.2 requirement comes from ``argparse``. ``format()`` with unnumbered

Please check for more locations, those were just the ones I found on a quick search.

[kartben]

A couple of more places needs to be updated as well:

Kconfiglib/README.rst

Lines 124 to 126 in 1e6f644

	Starting with Kconfiglib version 12.2.0, all utilities are compatible with both
	Python 2 and Python 3. Previously, ``menuconfig.py`` only ran under Python 3
	(i.e., it's now more backwards compatible than before).

Kconfiglib/README.rst

Line 36 in 1e6f644

implementation in Python 2/3. It started out as a helper library, but now has a

Kconfiglib/README.rst

Lines 167 to 174 in 1e6f644

	Python version compatibility (2.7/3.2+)
	~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
	Kconfiglib and all utilities run under both Python 2.7 and Python 3.2 and
	later. The code mostly uses basic Python features and has no third-party
	dependencies, so keeping it backwards-compatible is pretty low effort.
	The 3.2 requirement comes from ``argparse``. ``format()`` with unnumbered

Please check for more locations, those were just the ones I found on a quick search.

ouch, yes, "a couple" more indeed :) will actually move to draft as I suspect it might take me a few attempts to get everything right

[kartben]

@tejlmand - it should be better now! It was definitely more than "a couple" :)

[tejlmand]

Looks good 👍

Only some minor nits.

Have this PR been verified on Windows ?

[tejlmand]

should we mention that it might work on older Python versions, but this is not tested / guaranteed to work ?

[tejlmand]

I think keeping this comment make sense as it describes the reason for this construct.

Alternative, re-write the subprocess.run(...) to include universal_newlines=True and simplify this construct.

Side-note: seems the use of run() also means Python >=3.5 is now required 😉

[tejlmand]

How about adding universal_newlines=True ?