Detect non async driver on engine creation

An error is raised when creating an async engine with an
incompatible dbapi. Before the error was raised only when
first using the engine.

Change-Id: I977952b4c03ae51f568749ad744c545197bcd887
Reference: #5920

2 files changed, 6 insertions, 1 deletions

diff --git a/lib/sqlalchemy/exc.py b/lib/sqlalchemy/exc.py
index 289b8dfab..a0a86826d 100644
--- a/lib/sqlalchemy/exc.py
+++ b/lib/sqlalchemy/exc.py
@@ -287,7 +287,7 @@ class NoReferenceError(InvalidRequestError):
 
 class AwaitRequired(InvalidRequestError):
     """Error raised by the async greenlet spawn if no async operation
-    was awaited when it required one
+    was awaited when it required one.
 
     """
 
diff --git a/lib/sqlalchemy/ext/asyncio/engine.py b/lib/sqlalchemy/ext/asyncio/engine.py
index aa7e60dfb..db95ab371 100644
--- a/lib/sqlalchemy/ext/asyncio/engine.py
+++ b/lib/sqlalchemy/ext/asyncio/engine.py
@@ -527,6 +527,11 @@ class AsyncEngine(ProxyComparable, AsyncConnectable):
             await self.conn.close()
 
     def __init__(self, sync_engine: Engine):
+        if not sync_engine.dialect.is_async:
+            raise exc.InvalidRequestError(
+                "The asyncio extension requires an async driver to be used. "
+                f"The loaded {sync_engine.dialect.driver!r} is not async."
+            )
         self.sync_engine = self._proxied = sync_engine
 
     def begin(self):