Add missing DatabaseError definition

Author: kevin-yao

prestodb/exceptions.py

@@ -40,6 +40,10 @@ class PrestoError(Exception):
     pass
 
 
+class DatabaseError(Exception):
+    pass
+
+
 class PrestoQueryError(Exception):
     def __init__(self, error):
         self._error = error

prestodb/transaction.py

@@ -95,7 +95,7 @@ def commit(self):
         try:
             list(query.execute())
         except Exception as err:
-            raise prestodb.exceptions.DatabaseErrror(
+            raise prestodb.exceptions.DatabaseError(
                 'failed to commit transaction {}: {}'.format(self._id, err))
 
     def rollback(self):
@@ -104,5 +104,5 @@ def rollback(self):
         try:
             list(query.execute())
         except Exception as err:
-            raise prestodb.exceptions.DatabaseErrror(
+            raise prestodb.exceptions.DatabaseError(
                 'failed to rollback transaction {}: {}'.format(self._id, err))