[PATCH] Update tox.ini for python3.8 and fix pypy3.6

[Tomi Ollila]

On Mon, Jun 15 2020, David Bremner wrote:

> Floris Bruynooghe <flub at devork.be> writes:
>
>>  [testenv]
>>  deps =
>> @@ -14,3 +14,6 @@ commands = pytest --cov={envsitepackagesdir}/notmuch2 {posargs}
>>  
>>  [testenv:pypy35]
>>  basepython = pypy3.5
>> +
>> +[testenv:pypy36]
>> +basepython = pypy3.6
>
> I'm not an expert, but should python 3.7 and python 3.8 have similar
> clauses? Or do they work by default?

"Python 3.6 compatible PyPy3.6 v7.3.1" in https://www.pypy.org/download.html
hints there are not (yet) pypy3.7 nor pypy3.8

>
> d

Tomi