Skip the file if it has bad encoding.

Reported by Sean Canavan on docs@p.o.

Call asyncore.close_all() with ignore_all=True in the tearDown()
method of the test_asyncore base test case. It should prevent keeping
alive sockets in asyncore.socket_map if close() fails with an
unexpected error.

Revert also an unwanted change of my previous commit: remove name
parameter of Thread in test_quick_connect().

Skip test_normalization.test_main() if download raises a permission
error.

Buildbots don't run tests with -vv and so only log "xxx was modified
by test_xxx" which is not enough to debug such random issue. In many
cases, I'm unable to reproduce the warning and so unable to fix it.

Always logging the value before and value after should help to debug
such warning on buildbots.

Don't use addCleanup() in test_quick_connect() because it keeps the
Thread object alive and so @reap_threads fails on its timeout of 1
second. "./python -m test -v test_asyncore -m test_quick_connect"
now takes 185 ms, instead of 11 seconds.

Other minor changes:

* Use "with sock:" to close the socket instead of
  try/finally: sock.close()
* Use self.skipTest() in test_quick_connect() to remove one
  indentation level and notice user that the test is specific to
  AF_INET and AF_INET6

Revert f50354ad: it introduced a
regression in test_threadedtempfile.

instruction offsets.

Add tests for widths of opcode names.

raised an error.

Replace them with using concrete types API that never fails if appropriate.

* bpo-29514: Check magic number for micro release

Add a dict importlib.util.EXPECTED_MAGIC_NUMBERS which
details the initial and expected pyc magic number for
each minor release. This gives a mechanism for users to
check if the magic number has changed within a release and
for a test to ensure procedure is followed if a change is
necessary.

Add a test to check the current MAGIC_NUMBER against the
expected number for the release if the current release is
at candidate or final level. On test failure, describe to
the developer the procedure for changing the magic number.

* Simplify magic number release test

Simplify the magic number release test by removing
EXPECTED_MAGIC_NUMBERS table and making the expected
magic number self-contained within the test.

BPO: 29514

* Improve magic number test execution and message

Improve the execution of the magic number test by
using skipUnless for alpha and beta releases, and
directly inheriting from unittest.TestCase rather than
using the machinery for the other tests. Also improve
the error message to explain the reason for caution in
changing the magic number.

BPO: 29514

Negative result should be returned only when an error is set.

* Remove conditional on free of `dps`, since `dps` is now allocated for
all versions of OpenSSL
* Remove call to `x509_check_ca` since it was only used to cache
the `crldp` field of the certificate
CRL_DIST_POINTS_free is available in all supported versions of OpenSSL
(recent 0.9.8+) and LibreSSL.

Replace the deprecated AC_TRY_RUN with AC_RUN_IFELSE. Also, standardize the
variable name and allow for caching of the result.

* Allow underscores in numeric literals in lib2to3.
* Stricter literal parsing for Python 3.6 in lib2to3.pgen2.tokenize.
* Add test case for underscores in literals in Python 3.

Replace `For object's ... ` with `For objects ...`

And fix the parameter name.