* 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 b907abc8)

* 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 f6ebd838)

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

(cherry picked from commit a3a01a2f)

* 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 ad7eaed5)

* 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 92b1f901)