make URL immutable

it's not really correct that URL is mutable and doesn't do
any argument checking.   propose replacing it with an immutable
named tuple with rich copy-and-mutate methods.

At the moment this makes a hard change to the CreateEnginePlugin
docs that previously recommended url.query.pop().  I can't find
any plugins on github other than my own that are using this
feature, so see if we can just make a hard change on this one.

Fixes: #5526
Change-Id: I28a0a471d80792fa8c28f4fa573d6352966a4a79

1 files changed, 1 insertions, 1 deletions

diff --git a/lib/sqlalchemy/testing/assertsql.py b/lib/sqlalchemy/testing/assertsql.py
index c86e26ccf..e20209ba5 100644
--- a/lib/sqlalchemy/testing/assertsql.py
+++ b/lib/sqlalchemy/testing/assertsql.py
@@ -83,7 +83,7 @@ class CompiledSQL(SQLMatchRule):
                 params = {"implicit_returning": True}
             else:
                 params = {}
-            return url.URL(self.dialect).get_dialect()(**params)
+            return url.URL.create(self.dialect).get_dialect()(**params)
 
     def _received_statement(self, execute_observed):
         """reconstruct the statement and params in terms