Fix asynch error to comply with pep dbapi

clickhouse_sqlalchemy/drivers/asynch/base.py

@@ -1,5 +1,3 @@
-import asynch
-
 from sqlalchemy.sql.elements import TextClause
 from sqlalchemy.pool import AsyncAdaptedQueuePool
 
@@ -25,7 +23,7 @@ class ClickHouseDialect_asynch(ClickHouseDialect_native):
 
     @classmethod
     def import_dbapi(cls):
-        return AsyncAdapt_asynch_dbapi(asynch)
+        return AsyncAdapt_asynch_dbapi()
 
     @classmethod
     def get_pool_class(cls, url):

clickhouse_sqlalchemy/drivers/asynch/connector.py

@@ -1,5 +1,7 @@
 import asyncio
 
+import asynch
+import asynch.errors
 from sqlalchemy.engine.interfaces import AdaptedConnection
 from sqlalchemy.util.concurrency import await_only
 
@@ -109,15 +111,12 @@ def fetchall(self):
 
 
 class AsyncAdapt_asynch_dbapi:
-    def __init__(self, asynch):
-        self.asynch = asynch
+    def __init__(self):
         self.paramstyle = 'pyformat'
         self._init_dbapi_attributes()
 
-    class Error(Exception):
-        pass
-
     def _init_dbapi_attributes(self):
+        self.Error = asynch.errors.ClickHouseException
         for name in (
                 'ServerException',
                 'UnexpectedPacketFromServerError',
@@ -141,12 +140,12 @@ def _init_dbapi_attributes(self):
                 'ProgrammingError',
                 'NotSupportedError',
         ):
-            setattr(self, name, getattr(self.asynch.errors, name))
+            setattr(self, name, getattr(asynch.errors, name))
 
     def connect(self, *args, **kwargs) -> 'AsyncAdapt_asynch_connection':
         return AsyncAdapt_asynch_connection(
             self,
-            await_only(self.asynch.connect(*args, **kwargs))
+            await_only(asynch.connect(*args, **kwargs))
         )