[PATCH 1 of 5 STABLE] tests: invoke printenv.py via sh -c for test portability

[timeless]

timeless wrote:
> I'm sure this is already in, but wouldn't it be better to use a
> $PYTHON than `sh -c`?

FUJIWARA Katsunori wrote:
> I don't have strong opinion for using "sh -c".
>
> But, if we use $PYTHON instead of `sh -c` (= backing d19787db6fe0
> out), we should change many "sh -c 'printenv.py'" already existing in
> other test scenarios for similarity, too.
>
> Unfortunately, just replacing "sh -c" by $PYTHON can't be applied on
> some of them. For example, in test-hook.t:
>
>   $ cat > .hg/hgrc <<EOF
>   > [hooks]
...
>   > txnabort.1 = sh -c "HG_LOCAL= HG_TAG= printenv.py txnabort"
This looks like a candidate for:

env .... $PYTHON ...