this provides a front-end option to disable tests marked
as timing_intensive, all of which are in test_pool, which are more
fragile and aren't consistent on the
github runners.   also remove /reduce unnecessary time.sleep()
from two other pool tests that are not timing intensive.

note that this removes test_hanging_connect_within_overflow
from the github runs via the timing_intensive requirement.

I've also removed MockReconnectTest from exclusions as those are
really important tests and they use mocks so should not have
platform dependent issues.   Need to see what the
windows failures are.

Closes: #5633
Pull-request: https://github.com/sqlalchemy/sqlalchemy/pull/5633
Pull-request-sha: 166833e16ec342dfa10edb287d7aa495ddd1b59d

Change-Id: Icb3d284a2a952e2495d80fa91e22e0b32a54340f

We want TOX_POSTGRESQL and similar to be the fixed variable
that is configured from CI environment.   These variables should refer
to database servers but individual drivers like asyncpg mysqlconnector
etc. should come from local tox.ini.  add a new system to generate
per-driver URLs from a simple list of hostname-based URLs delivered
from CI environment.

Change-Id: I4267b4a70742765388c7e7c4432c1da9d9adece2

Using the approach introduced at
https://gist.github.com/zzzeek/6287e28054d3baddc07fa21a7227904e

We can now create asyncio endpoints that are then handled
in "implicit IO" form within the majority of the Core internals.
Then coroutines are re-exposed at the point at which we call
into asyncpg methods.

Patch includes:

* asyncpg dialect

* asyncio package

* engine, result, ORM session classes

* new test fixtures, tests

* some work with pep-484 and a short plugin for the
  pyannotate package, which seems to have so-so results

Change-Id: Idbcc0eff72c4cad572914acdd6f40ddb1aef1a7d
Fixes: #3414

Added support for "CREATE SEQUENCE" and full :class:`.Sequence` support for
Microsoft SQL Server.  This removes the deprecated feature of using
:class:`.Sequence` objects to manipulate IDENTITY characteristics which
should now be performed using ``mssql_identity_start`` and
``mssql_identity_increment`` as documented at :ref:`mssql_identity`. The
change includes a new parameter :paramref:`.Sequence.data_type` to
accommodate SQL Server's choice of datatype, which for that backend
includes INTEGER and BIGINT.   The default starting value for SQL Server's
version of :class:`.Sequence` has been set at 1; this default is now
emitted within the CREATE SEQUENCE DDL for all backends.

Fixes: #4235
Fixes: #4633
Change-Id: I6aa55c441e8146c2f002e2e201a7f645e667b916

Change-Id: Ib256ae34de15d29ee9a48e3be86073610f8d1a65

step one, do away with __connection attribute and using
awkward AttributeError logic

step two, move all management of "connection._transaction"
into the transaction objects themselves where it's easier
to follow.

build MarkerTransaction that takes the role of
"do-nothing block"

new connection datamodel is: connection._transaction, always
a root, connection._nested_transaction, always a nested.

nested transactions still chain to each other as this
is still sort of necessary but they consider the root
transaction separately, and the marker transactions
not at all.

introduce new InvalidRequestError subclass
PendingRollbackError.  Apply to connection and session
for all cases where a transaction needs to be rolled
back before continuing.   Within Connection,
both PendingRollbackError as well as ResourceClosedError
are now raised directly without being handled by
handle_dbapi_error();  this removes these two exception
cases from the handle_error event handler as well as
from StatementError wrapping, as these two exceptions are
not statement oriented and are instead programmatic
issues, that the application is failing to handle database
errors properly.

Revise savepoints so that when a release fails, they set
themselves as inactive so that their rollback() method
does not throw another exception.

Give savepoints another go on MySQL, can't get release working
however get support for basic round trip going

Fixes: #5327
Change-Id: Ia3cbbf56d4882fcc7980f90519412f1711fae74d

Change-Id: I431e1ef41e26d490343204a75a5c097768749768

Change-Id: I08440dc25e40ea1ccea1778f6ee9e28a00808235

- ensure we escape out percent signs when a CompiledSQL or RegexSQL
has percent signs in the SQL or in the parameter repr

- to support combinations, print out complete test name in skip
messages, py.test environment gives us a way to do this

Change-Id: Ia9e62f7c1026c1465986144c5757e35fc164a2b8

Dialect tests tend to have a lot of lists of types,
SQL constructs etc, convert as many of these to @combinations
as possible.

This is exposing that we don't have per-combination
exclusion rules set up which is making things a little bit
cumbersome.

Also set up a fixture that does metadata + DDL.

Change-Id: Ief820e48c9202982b0b1e181b87862490cd7b0c3