[3.6] bpo-30871: Add test.pythoninfo (#3174)

[3.6] bpo-30871: Add test.pythoninfo (#3174)

* bpo-30871: Add test.pythoninfo (#3075)

* Add Lib/test/pythoninfo.py: script collecting various informations
  about Python to help debugging test failures.
* regrtest: remove sys.hash_info and sys.flags from header.
* Travis CI, Appveyor: run pythoninfo before tests
(cherry picked from commit b907abc88589f7bea52c5afe172ececc6edcda70)

* bpo-30871: pythoninfo: add expat and _decimal (#3121)

* bpo-30871: pythoninfo: add expat and _decimal

* Remove _decimal.__version__

The string is hardcoded, not really interesting.

(cherry picked from commit f6ebd838f00b4c211c72d85ee49749e910cd3afe)

* bpo-30871: Add "make pythoninfo" (#3120)

(cherry picked from commit a3a01a2fceab2188b282ab9911f79c99a4c32273)

* bpo-30871: pythoninfo: more sys, os, time data (#3130)

* bpo-30871: pythoninfo: more sys, os, time data

PythonInfo now converts types other than intger to string by default.

* fix typo

(cherry picked from commit ad7eaed54382b346784e51a6f0122ce81e8842b5)

* bpo-31231: Fix pythoninfo in Travis config (#3134)

bpo-31231, bpo-30871: Replace "./python -m test.pythoninfo" with
"make pythoninfo", since macOS uses ./python.exe.
(cherry picked from commit 92b1f90143286385c0ff5be98d3721b90580a912)