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.

Reported by Lucio Ricardo Montero Valenzuela.

multiple times.  Writing to closed zip entry writer object now always produce
a ValueError.

The data contained in them is nonsensical

contextlib._GeneratorContextManager.__exit__ includes a special case to deal with
PEP 479 RuntimeErrors created when `StopIteration` is thrown into the context
manager body.

Previously this check was too permissive, and undid one level of chaining on *all*
RuntimeError instances, not just those that wrapped a StopIteration instance.

The reference to administrative data was confusing to readers,
so this simplifies the note to explain that deep copying may copy
more then you intended, such as data that you expected to be
shared between copies.

conn.set_trace_callback() shouldn't be called multiple times when the
schema is changing.

This has indirectly been fixed by using sqlite3_prepare_v2() in bpo-9303.

The original attempted fix missed an `isdir()` call in
`get_base_branch()`.

Also changed format specifier for function name from "%s" to "%.200s"
and exception messages should start with lowercase letter.

Documents a few omitted classes and adds NamedTuple methods.