bpo-15386, bpo-37473: test_import, regrtest and libregrtest no longer
import importlib as soon as possible, as the first import, "to test
bpo-15386".
It is tested by test_import.test_there_can_be_only_one().
Sort test_import imports.
When running the test suite using --use=all / -u all, exclude tzdata
since it makes test_datetime too slow (15-20 min on some buildbots)
which then times out on some buildbots.
-u tzdata must now be enabled explicitly, -u tzdata or -u all,tzdata,
to run all test_datetime tests.
Fix also regrtest command line parser to allow passing -u
extralargefile to run test_zipfile64.
Travis CI: remove -tzdata. Replace -u all,-tzdata,-cpu with -u all,-cpu since tzdata is now excluded from -u all.
* Rename libregrtest.main_in_temp_cwd() to libregrtest.main()
* Add regrtest.main_in_temp_cwd() alias to libregrtest.main()
* Move old main_in_temp_cwd() code into libregrtest.Regrtest.main()
* Update multiple scripts to call libregrtest.main()
Start to split regrtest.py into smaller parts with the creation of
Lib/test/libregrtest/cmdline.py: code to handle the command line, especially
parsing command line arguments. This part of the code is tested by
test_regrtest.