Detect non compatible execution in async mode

The SQLAlchemy async mode now detects and raises an informative
error when an non asyncio compatible :term:`DBAPI` is used.
Using a standard ``DBAPI`` with async SQLAlchemy will cause
it to block like any sync call, interrupting the executing asyncio
loop.

Change-Id: I9aed87dc1b0df53e8cb2109495237038aa2cb2d4

1 files changed, 9 insertions, 4 deletions

diff --git a/lib/sqlalchemy/exc.py b/lib/sqlalchemy/exc.py
index 7ba2e369b..63c56c34d 100644
--- a/lib/sqlalchemy/exc.py
+++ b/lib/sqlalchemy/exc.py
@@ -285,6 +285,15 @@ class NoReferenceError(InvalidRequestError):
     """Raised by ``ForeignKey`` to indicate a reference cannot be resolved."""
 
 
+class AwaitRequired(InvalidRequestError):
+    """Error raised by the async greenlet spawn if no async operation
+    was awaited when it required one
+
+    """
+
+    code = "xd1r"
+
+
 class NoReferencedTableError(NoReferenceError):
     """Raised by ``ForeignKey`` when the referred ``Table`` cannot be
     located.
@@ -355,10 +364,6 @@ class DontWrapMixin(object):
     """
 
 
-# Moved to orm.exc; compatibility definition installed by orm import until 0.6
-UnmappedColumnError = None
-
-
 class StatementError(SQLAlchemyError):
     """An error occurred during execution of a SQL statement.