Implement rudimentary asyncio support w/ asyncpg

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

1 files changed, 4 insertions, 0 deletions

diff --git a/doc/build/conf.py b/doc/build/conf.py
index 13d573296..d4fdf58a0 100644
--- a/doc/build/conf.py
+++ b/doc/build/conf.py
@@ -106,6 +106,9 @@ autodocmods_convert_modname = {
     "sqlalchemy.engine.row": "sqlalchemy.engine",
     "sqlalchemy.engine.cursor": "sqlalchemy.engine",
     "sqlalchemy.engine.result": "sqlalchemy.engine",
+    "sqlalchemy.ext.asyncio.result": "sqlalchemy.ext.asyncio",
+    "sqlalchemy.ext.asyncio.engine": "sqlalchemy.ext.asyncio",
+    "sqlalchemy.ext.asyncio.session": "sqlalchemy.ext.asyncio",
     "sqlalchemy.util._collections": "sqlalchemy.util",
     "sqlalchemy.orm.relationships": "sqlalchemy.orm",
     "sqlalchemy.orm.interfaces": "sqlalchemy.orm",
@@ -128,6 +131,7 @@ zzzeeksphinx_module_prefixes = {
     "_row": "sqlalchemy.engine",
     "_schema": "sqlalchemy.schema",
     "_types": "sqlalchemy.types",
+    "_asyncio": "sqlalchemy.ext.asyncio",
     "_expression": "sqlalchemy.sql.expression",
     "_sql": "sqlalchemy.sql.expression",
     "_dml": "sqlalchemy.sql.expression",