includes adjustment to setup.py to recognize __version__ correctly

The :class:`.URL` object now allows query keys to be specified multiple
times where their values will be joined into a list.  This is to support
the plugins feature documented at :class:`.CreateEnginePlugin` which
documents that "plugin" can be passed multiple times. Additionally, the
plugin names can be passed to :func:`.create_engine` outside of the URL
using the new :paramref:`.create_engine.plugins` parameter.

Change-Id: Ifc48ad120bd6c6204eda567492caf79832aeeaa5
Fixes: #4170

The "password" attribute of the :class:`.url.URL` object can now be
any user-defined or user-subclassed string object that responds to the
Python ``str()`` builtin.   The object passed will be maintained as the
datamember :attr:`.url.URL.password_original` and will be consulted
when the :attr:`.url.URL.password` attribute is read to produce the
string value.

Change-Id: I91d101c3b10e135ae7e4de60a5104b51776db84f
Fixes: #4089

tested using pycodestyle version 2.2.0

Fixes: #3885
Change-Id: I5df43adc3aefe318f9eeab72a078247a548ec566
Pull-request: https://github.com/zzzeek/sqlalchemy/pull/343

- add a connect=True key to connection record to support
  pre-loading of _ConnectionRecord objects
- ensure _ConnectionRecord.close() leaves the record in a good
  state for reopening
- add _ConnectionRecord.record_info for persistent storage
- add "in_use" accessor based on fairy_ref being present or not
- allow for the exclusions system and SuiteRequirements to be
  usable without the full plugin_base setup.
- move some Python-env requirements to the importable
  requirements.py module.
- allow starttime to be queried
- add additional events for engine plugins
- have "dialect" be a first-class parameter to the pool,
  ensure the engine strategy supplies it up front

Change-Id: Ibf549f7a1766e49d335cd6f5e26bacfaef9a8229

be stated in the query string for a URL.   Custom plugins can
be written which will be given the chance up front to alter and/or
consume the engine's URL and keyword arguments, and then at engine
create time will be given the engine itself to allow additional
modifications or event registration.  Plugins are written as a
subclass of :class:`.CreateEnginePlugin`; see that class for
details.
fixes #3536

:func:`.engine_from_config` were not being parsed correctly;
these included ``pool_threadlocal`` and the psycopg2 argument
``use_native_unicode``. fixes #3435
- add legacy_schema_aliasing config parsing for mssql
- move use_native_unicode config arg to the psycopg2 dialect

functionality.   Added a new "soft invalidate" feature to the
connection pool at the level of the checked out connection wrapper
as well as the :class:`._ConnectionRecord`.  This works similarly
to a modern pool invalidation in that connections aren't actively
closed, but are recycled only on next checkout; this is essentially
a per-connection version of that feature.  A new event
:class:`.PoolEvents.soft_invalidate` is added to complement it.
fixes #3379

- Added new flag
:attr:`.ExceptionContext.invalidate_pool_on_disconnect`.
Allows an error handler within :meth:`.ConnectionEvents.handle_error`
to maintain a "disconnect" condition, but to handle calling invalidate
on individual connections in a specific manner within the event.

- Added new event :class:`.DialectEvents.do_connect`, which allows
interception / replacement of when the :meth:`.Dialect.connect`
hook is called to create a DBAPI connection.  Also added
dialect plugin hooks :meth:`.Dialect.get_dialect_cls` and
:meth:`.Dialect.engine_created` which allow external plugins to
add events to existing dialects using entry points.
fixes #3355

:paramref:`.Pool.reset_on_return` parameter as a synonym for ``None``,
so that string values can be used for all settings, allowing
.ini file utilities like :func:`.engine_from_config` to be usable
without issue.
fixes #3375