Require the SQLAlchemy URI on the database model (#8720)

* Require the SQLAlchemy URI when creating a database

* Add migration to make dbs.sqlalchemy_uri not-nullable

* Fixes for black, isort, tests

* Alter migration to use current revision from master as downgrade target

* Update tests to support new db constraint

* black

tests/base_tests.py

@@ -228,6 +228,7 @@ class SupersetTestCase(TestCase):
             cls=models.Database,
             criteria={"database_name": database_name},
             session=db.session,
+            sqlalchemy_uri="sqlite://test",
             id=db_id,
             extra=extra,
         )

tests/security_tests.py

@@ -316,7 +316,9 @@ class RolePermissionTests(SupersetTestCase):
 
     def test_set_perm_database(self):
         session = db.session
-        database = Database(database_name="tmp_database")
+        database = Database(
+            database_name="tmp_database", sqlalchemy_uri="sqlite://test"
+        )
         session.add(database)
 
         stored_db = (
@@ -346,7 +348,9 @@ class RolePermissionTests(SupersetTestCase):
 
     def test_set_perm_slice(self):
         session = db.session
-        database = Database(database_name="tmp_database")
+        database = Database(
+            database_name="tmp_database", sqlalchemy_uri="sqlite://test"
+        )
         table = SqlaTable(table_name="tmp_perm_table", database=database)
         session.add(database)
         session.add(table)