ISO C90 forbids mixed declarations and code

ISO C90 forbids mixed declarations and code

Reported by Arfrever Frehtes Taifersar Arahesis.

faulthandler._read_null() is not reliable: it does not crash on AIX.

faulthandler._read_null() is not reliable: it does not crash on AIX.

sigwaitinfo() can be interrupted on Linux (raises InterruptedError), but not on
AIX.

sigwaitinfo() can be interrupted on Linux (raises InterruptedError), but not on
AIX.

locale.getlocale(name) in test.regrtest.saved_test_environment

locale.getlocale() parses the locale, which is useless for
saved_test_environment.

Skip LC_ALL becore getlocale(locale.LC_ALL) always fail, and catch also
ValueError.

get_ca_list() lists all loaded CA certificates and cert_store_stats() returns
amount of loaded X.509 certs, X.509 CA certs and CRLs.

when \r\n appears at end of 65535 bytes without other newlines.

when \r\n appears at end of 65535 bytes without other newlines.

in ASN1_TIME fields.

* Use mixins for generating tests for different compression types.
* Make test_tarfile discoverable.
* Use more special tests (i.e. assertEqual, assertIs) instead of assertTrue.
* Add explicit test skips instead of reporting skipped tests as passed.
* Wrap long lines.
* Correct a comment for test_hardlink_extraction1.
* Add support.requires_gzip.
* Replace ImportError by  ModuleNotFoundError.

and some other minor enhancements.

* Use mixins for generating tests for different compression types.
* Make test_tarfile discoverable.
* Use more special tests (i.e. assertEqual, assertIs) instead of assertTrue.
* Add explicit test skips instead of reporting skipped tests as passed.
* Wrap long lines.
* Correct a comment for test_hardlink_extraction1.
* Add support.requires_gzip.

and some other minor enhancements.